Chapter 21 Standard Template Library STL Outline 21

Chapter 21 - Standard Template Library (STL) Outline 21. 1 21. 2 21. 3 21. 4 Introduction to the Standard Template Library (STL) 21. 1. 1 Introduction to Containers 21. 1. 2 Introduction to Iterators 21. 1. 3 Introduction to Algorithms Sequence Containers 21. 2. 1 vector Sequence Container 21. 2. 2 list Sequence Container 21. 2. 3 deque Sequence Container Associative Containers 21. 3. 1 multiset Associative Container 21. 3. 2 set Associative Container 21. 3. 3 multimap Associative Container 21. 3. 4 map Associative Container Adapters 21. 4. 1 stack Adapter 21. 4. 2 queue Adapter 21. 4. 3 priority_queue Adapter 2003 Prentice Hall, Inc. All rights reserved. 1

Chapter 21 - Standard Template Library (STL) 21. 5 21. 6 21. 7 Algorithms 21. 5. 1 fill, fill_n, generate and generate_n 21. 5. 2 equal, mismatch and lexicographical_compare 21. 5. 3 remove, remove_if, remove_copy and remove_copy_if 21. 5. 4 replace, replace_if, replace_copy and replace_copy_if 21. 5. 5 Mathematical Algorithms 21. 5. 6 Basic Searching and Sorting Algorithms 21. 5. 7 swap, iter_swap and swap_ranges 21. 5. 8 copy_backward, merge, unique and reverse 21. 5. 9 inplace_merge, unique_copy and reverse_copy 21. 5. 10 Set Operations 21. 5. 11 lower_bound, upper_bound and equal_range 21. 5. 12 Heapsort 21. 5. 13 min and max 21. 5. 14 Algorithms Not Covered in This Chapter Class bitset Function Objects 2003 Prentice Hall, Inc. All rights reserved. 2

21. 1 Introduction to the Standard Template Library (STL) • STL – Powerful, template-based components • Containers: template data structures • Iterators: like pointers, access elements of containers • Algorithms: data manipulation, searching, sorting, etc. – Object- oriented programming: reuse, reuse – Only an introduction to STL, a huge class library 2003 Prentice Hall, Inc. All rights reserved. 3

4 21. 1. 1 Introduction to Containers • Three types of containers – Sequence containers • Linear data structures (vectors, linked lists) • First-class container – Associative containers • Non-linear, can find elements quickly • Key/value pairs • First-class container – Container adapters • Near containers – Similar to containers, with reduced functionality • Containers have some common functions 2003 Prentice Hall, Inc. All rights reserved.

5 STL Container Classes (Fig. 21. 1) • Sequence containers – vector – deque – list • Associative containers – – set multiset map multimap • Container adapters – stack – queue – priority_queue 2003 Prentice Hall, Inc. All rights reserved.

6 Common STL Member Functions (Fig. 21. 2) • Member functions for all containers – – – Default constructor, copy constructor, destructor empty max_size, size = < <= > >= == != swap • Functions for first-class containers – begin, end – rbegin, rend – erase, clear 2003 Prentice Hall, Inc. All rights reserved.

7 Common STL typedefs (Fig. 21. 4) • typedefs for first-class containers – – – – – value_type reference const_reference pointer iterator const_iterator reverse_iterator const_reverse_iterator difference_type size_type 2003 Prentice Hall, Inc. All rights reserved.

8 21. 1. 2 Introduction to Iterators • Iterators similar to pointers – Point to first element in a container – Iterator operators same for all containers • * dereferences • ++ points to next element • begin() returns iterator to first element • end() returns iterator past last element – Use iterators with sequences (ranges) • Containers • Input sequences: istream_iterator • Output sequences: ostream_iterator 2003 Prentice Hall, Inc. All rights reserved.

9 21. 1. 2 Introduction to Iterators • Usage – std: : istream_iterator< int > input. Int( cin ) • Can read input from cin • *input. Int – Dereference to read first int from cin • ++input. Int – Go to next in stream – std: : ostream_iterator< int > output. Int(cout) • Can output ints to cout • *output. Int = 7 – Outputs 7 to cout • ++output. Int – Advances iterator so we can output next int 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 5: fig 21_05. cpp // Demonstrating input and output with iterators. #include <iostream> 4 5 6 7 using std: : cout; using std: : cin; using std: : endl; 8 9 #include <iterator> 10 11 12 13 int main() { cout << "Enter two Outline fig 21_05. cpp (1 of 2) Note creation of istream_iterator. For compilation reasons, we use std: : rather than a using integers: "; statement. // ostream_iterator and istream_iterator 14 15 16 // create istream_iterator for reading int values from cin std: : istream_iterator< int > input. Int( cin ); 17 18 19 20 int number 1 = *input. Int; // read int from standard input ++input. Int; // move iterator to next input value int number 2 = *input. Int; // read int from standard input Access and assign the iterator like a pointer. 21 2003 Prentice Hall, Inc. All rights reserved. 10

22 23 // create ostream_iterator for writing int values to cout std: : ostream_iterator< int > output. Int( cout ); 24 25 26 27 cout << "The sum is: "; *output. Int = number 1 + number 2; cout << endl; 28 29 return 0; 30 31 // output result to cout Outline fig 21_05. cpp (2 of 2) fig 21_05. cpp output (1 of 1) } // end main Enter two integers: 12 25 The sum is: 37 Create an ostream_iterator is similar. Assigning to this iterator outputs to cout. 2003 Prentice Hall, Inc. All rights reserved. 11

12 Iterator Categories (Fig. 21. 6) • Input – Read elements from container, can only move forward • Output – Write elements to container, only forward • Forward – Combines input and output, retains position – Multi-pass (can pass through sequence twice) • Bidirectional – Like forward, but can move backwards as well • Random access – Like bidirectional, but can also jump to any element 2003 Prentice Hall, Inc. All rights reserved.

13 Iterator Types Supported (Fig. 21. 8) • Sequence containers – vector: random access – deque: random access – list: bidirectional • Associative containers (all bidirectional) – – set multiset Map multimap • Container adapters (no iterators supported) – stack – queue – priority_queue 2003 Prentice Hall, Inc. All rights reserved.

14 Iterator Operations (Fig. 21. 10) • All – ++p, p++ • Input iterators – *p – p = p 1 – p == p 1, p != p 1 • Output iterators – *p – p = p 1 • Forward iterators – Have functionality of input and output iterators 2003 Prentice Hall, Inc. All rights reserved.

15 Iterator Operations (Fig. 21. 10) • Bidirectional – --p, p-- • Random access – – – p + i, p += i p - i, p -= i p[i] p < p 1, p <= p 1 p > p 1, p >= p 1 2003 Prentice Hall, Inc. All rights reserved.

16 21. 1. 3 Introduction to Algorithms • STL has algorithms used generically across containers – Operate on elements indirectly via iterators – Often operate on sequences of elements • Defined by pairs of iterators • First and last element – Algorithms often return iterators • find() • Returns iterator to element, or end() if not found – Premade algorithms save programmers time and effort 2003 Prentice Hall, Inc. All rights reserved.

17 21. 2 Sequence Containers • Three sequence containers – vector - based on arrays – deque - based on arrays – list - robust linked list 2003 Prentice Hall, Inc. All rights reserved.

18 21. 2. 1 vector Sequence Container • vector – <vector> – Data structure with contiguous memory locations • Access elements with [] – Use when data must be sorted and easily accessible • When memory exhausted – Allocates larger, contiguous area of memory – Copies itself there – Deallocates old memory • Has random access iterators 2003 Prentice Hall, Inc. All rights reserved.

19 21. 2. 1 vector Sequence Container • Declarations – std: : vector <type> v; • type: int, float, etc. • Iterators – std: : vector<type>: : const_iterator iter. Var; • const_iterator cannot modify elements – std: : vector<type>: : reverse_iterator iter. Var; • Visits elements in reverse order (end to beginning) • Use rbegin to get starting point • Use rend to get ending point 2003 Prentice Hall, Inc. All rights reserved.

20 21. 2. 1 vector Sequence Container • vector functions – v. push_back(value) • Add element to end (found in all sequence containers). – v. size() • Current size of vector – v. capacity() • How much vector can hold before reallocating memory • Reallocation doubles size – vector<type> v(a, a + SIZE) • Creates vector v with elements from array a up to (not including) a + SIZE 2003 Prentice Hall, Inc. All rights reserved.

21 21. 2. 1 vector Sequence Container • vector functions – v. insert(iterator, value ) • Inserts value before location of iterator – v. insert(iterator, array + SIZE) • Inserts array elements (up to, but not including array + SIZE) into vector – v. erase( iterator ) • Remove element from container – v. erase( iter 1, iter 2 ) • Remove elements starting from iter 1 and up to (not including) iter 2 – v. clear() • Erases entire container 2003 Prentice Hall, Inc. All rights reserved.

22 21. 2. 1 vector Sequence Container • vector functions operations – v. front(), v. back() • Return first and last element – v[element. Number] = value; • Assign value to an element – v. at(element. Number) = value; • As above, with range checking • out_of_bounds exception 2003 Prentice Hall, Inc. All rights reserved.

23 21. 2. 1 vector Sequence Container • ostream_iterator – std: : ostream_iterator< type > Name( output. Stream, separator ); • type: outputs values of a certain type • output. Stream: iterator output location • separator: character separating outputs • Example – std: : ostream_iterator< int > output( cout, " " ); – std: : copy( iterator 1, iterator 2, output ); • Copies elements from iterator 1 up to (not including) iterator 2 to output, an ostream_iterator 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 14: fig 21_14. cpp // Demonstrating standard library vector class template. #include <iostream> 4 5 6 7 using std: : cout; using std: : cin; using std: : endl; 8 9 #include <vector> 10 11 12 13 // prototype for function template print. Vector template < class T > void print. Vector( const std: : vector< T > &integers 2 ); 14 15 16 17 18 int main() { Create a const int SIZE = 6; int array[ SIZE ] = { 1, 2, 3, 4, 5, 6 }; Outline fig 21_14. cpp (1 of 3) // vector class-template definition 19 20 std: : vector< int > integers; 21 22 23 24 25 cout << << vector of ints. Call member functions. "The initial size of integers is: " integers. size() "n. The initial capacity of integers is: " integers. capacity(); 26 2003 Prentice Hall, Inc. All rights reserved. 24

27 28 29 30 // function push_back integers. push_back( 2 integers. push_back( 3 integers. push_back( 4 31 32 33 34 cout << "n. The size of integers is: " << integers. size() << "n. The capacity of integers is: " << integers. capacity(); 35 36 cout << "nn. Output array using pointer notation: " ; 37 38 39 for ( int *ptr = array; ptr != array + SIZE; ++ptr ) cout << *ptr << ' '; 40 41 42 cout << "n. Output vector using iterator notation: " ; print. Vector( integers ); 43 44 cout << "n. Reversed contents of vector integers: " ; is in every sequence collection ); ); ); Add elements to end of Outline vector using push_back. fig 21_14. cpp (2 of 3) 45 2003 Prentice Hall, Inc. All rights reserved. 25

46 std: : vector< int >: : reverse_iterator reverse. Iterator; 47 48 49 50 51 for ( reverse. Iterator = integers. rbegin(); reverse. Iterator!= integers. rend(); ++reverse. Iterator ) cout << *reverse. Iterator << ' '; 52 53 cout << endl; 54 55 return 0; 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 } // end main // function template for outputting vector elements template < class T > void print. Vector( const std: : vector< T > &integers 2 ) { std: : vector< T >: : const_iterator const. Iterator; Outline Walk through vector fig 21_14. cpp backwards using (3 of 3) a reverse_iterator. Template function to walk through vector forwards. for ( const. Iterator = integers 2. begin(); const. Iterator != integers 2. end(); const. Iterator++ ) cout << *const. Iterator << ' '; } // end function print. Vector 2003 Prentice Hall, Inc. All rights reserved. 26

The The initial size of v is: 0 initial capacity of v is: 0 size of v is: 3 capacity of v is: 4 Contents of array a using pointer notation: 1 2 3 4 5 6 Contents of vector v using iterator notation: 2 3 4 Reversed contents of vector v: 4 3 2 Outline fig 21_14. cpp output (1 of 1) 2003 Prentice Hall, Inc. All rights reserved. 27

1 2 3 4 // Fig. 21. 15: fig 21_15. cpp // Testing Standard Library vector class template // element-manipulation functions. #include <iostream> 5 6 7 using std: : cout; using std: : endl; 8 9 10 #include <vector> #include <algorithm> 11 12 13 14 15 int main() { const int SIZE = 6; int array[ SIZE ] = { 1, 2, 3, 4, 5, 6 }; Outline fig 21_15. cpp (1 of 3) // vector class-template definition // copy algorithm Create vector (initialized using an array) and ostream_iterator. 16 17 18 std: : vector< int > integers( array, array + SIZE ); std: : ostream_iterator< int > output( cout, " " ); 19 20 21 cout << "Vector integers contains: " ; std: : copy( integers. begin(), integers. end(), output ); 22 23 24 cout << "n. First element of integers: " << integers. front() << "n. Last element of integers: " << integers. back(); Copy range of iterators to output (ostream_iterator). 25 2003 Prentice Hall, Inc. All rights reserved. 28

26 27 integers[ 0 ] = 7; integers. at( 2 ) = 10; 28 29 30 // insert 22 as 2 nd element integers. insert( integers. begin() + 1, 22 ); 31 32 33 cout << "nn. Contents of vector integers after changes: " ; std: : copy( integers. begin(), integers. end(), output ); 34 35 36 37 // access out-of-range element try { integers. at( 100 ) = 777; 38 39 } // end try 40 41 42 43 // catch out_of_range exception catch ( std: : out_of_range out. Of. Range ) { cout << "nn. Exception: " << out. Of. Range. what(); 44 45 } // end catch 46 47 48 49 50 // erase first element integers. erase( integers. begin() ); cout << "nn. Vector integers after erasing first element: " ; std: : copy( integers. begin(), integers. end(), output ); // set first element to 7 // set element at position 2 to 10 Outline More vector member fig 21_15. cpp functions. (2 of 3) at has range checking, and can throw an exception. 51 2003 Prentice Hall, Inc. All rights reserved. 29

52 53 54 55 // erase remaining elements integers. erase( integers. begin(), integers. end() ); cout << "n. After erasing all elements, vector integers " << ( integers. empty() ? "is" : "is not" ) << " empty"; 56 57 58 59 60 // insert elements from array integers. insert( integers. begin(), array + SIZE ); cout << "nn. Contents of vector integers before clear: " ; std: : copy( integers. begin(), integers. end(), output ); 61 62 63 64 65 // empty integers; clear calls erase to empty a collection integers. clear(); cout << "n. After clear, vector integers " << ( integers. empty() ? "is" : "is not" ) << " empty"; 66 67 cout << endl; 68 69 return 0; 70 71 Outline fig 21_15. cpp (3 of 3) } // end main 2003 Prentice Hall, Inc. All rights reserved. 30

Vector integers contains: 1 2 3 4 5 6 First element of integers: 1 Last element of integers: 6 Contents of vector integers after changes: 7 22 2 10 4 5 6 Exception: invalid vector<T> subscript Outline fig 21_15. cpp output (1 of 1) Vector integers after erasing first element: 22 2 10 4 5 6 After erasing all elements, vector integers is empty Contents of vector integers before clear: 1 2 3 4 5 6 After clear, vector integers is empty 2003 Prentice Hall, Inc. All rights reserved. 31

32 21. 2. 2 list Sequence Container • list container – – – Header <list> Efficient insertion/deletion anywhere in container Doubly-linked list (two pointers per node) Bidirectional iterators std: : list< type > name; 2003 Prentice Hall, Inc. All rights reserved.

33 21. 2. 2 list Sequence Container • list functions for object t – t. sort() • Sorts in ascending order – t. splice(iterator, other. Object ); • Inserts values from other. Object before iterator, removes other. Object – t. merge( other. Object ) • Removes other. Object and inserts it into t, sorted – t. unique() • Removes duplicate elements 2003 Prentice Hall, Inc. All rights reserved.

34 21. 2. 2 list Sequence Container • list functions – t. swap(other. Object); • Exchange contents – t. assign(iterator 1, iterator 2) • Replaces contents with elements in range of iterators – t. remove(value) • Erases all instances of value 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 17: fig 21_17. cpp // Standard library list class template test program. #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 9 #include <list> #include <algorithm> 10 11 12 13 // prototype for function template print. List template < class T > void print. List( const std: : list< T > &list. Ref ); 14 15 16 17 18 int main() { const int SIZE = 4; int array[ SIZE ] = { 2, 6, 4, 8 }; Outline fig 21_17. cpp (1 of 5) // list class-template definition // copy algorithm 19 20 21 std: : list< int > values; std: : list< int > other. Values; 22 23 24 25 26 27 // insert items in values. push_front( 1 ); values. push_front( 2 ); values. push_back( 4 ); values. push_back( 3 ); Create two list objects. 2003 Prentice Hall, Inc. All rights reserved. 35

28 29 30 cout << "values contains: "; print. List( values ); 31 32 values. sort(); 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 Various list member functions. // sort values Outline fig 21_17. cpp (2 of 5) cout << "nvalues after sorting contains: " ; print. List( values ); // insert elements of array into other. Values. insert( other. Values. begin(), array + SIZE ); cout << "n. After insert, other. Values contains: " ; print. List( other. Values ); // remove other. Values elements and insert at end of values. splice( values. end(), other. Values ); cout << "n. After splice, values contains: " ; print. List( values ); 49 50 values. sort(); 51 52 53 cout << "n. After sort, values contains: " ; print. List( values ); // sort values 54 2003 Prentice Hall, Inc. All rights reserved. 36

55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 // insert elements of array into other. Values. insert( other. Values. begin(), array + SIZE ); other. Values. sort(); cout << "n. After insert, other. Values contains: " ; print. List( other. Values ); Outline fig 21_17. cpp (3 of 5) // remove other. Values elements and insert into values // in sorted order values. merge( other. Values ); cout << "n. After merge: n values contains: " ; print. List( values ); cout << "n other. Values contains: " ; print. List( other. Values ); values. pop_front(); values. pop_back(); // remove element from front // remove element from back cout << "n. After pop_front and pop_back: " << "n values contains: " ; print. List( values ); values. unique(); // remove duplicate elements cout << "n. After unique, values contains: " ; print. List( values ); 2003 Prentice Hall, Inc. All rights reserved. 37

83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 // swap elements of values and other. Values values. swap( other. Values ); cout << "n. After swap: n values contains: " ; print. List( values ); cout << "n other. Values contains: " ; print. List( other. Values ); Outline fig 21_17. cpp (4 of 5) // replace contents of values with elements of other. Values values. assign( other. Values. begin(), other. Values. end() ); cout << "n. After assign, values contains: " ; print. List( values ); // remove other. Values elements and insert into values // in sorted order values. merge( other. Values ); cout << "n. After merge, values contains: " ; print. List( values ); values. remove( 4 ); // remove all 4 s cout << "n. After remove( 4 ), values contains: " ; print. List( values ); 2003 Prentice Hall, Inc. All rights reserved. 38

109 110 cout << endl; 111 112 return 0; 113 114 } // end main 115 116 117 118 119 120 121 122 // print. List function template definition; uses // ostream_iterator and copy algorithm to output list elements template < class T > void print. List( const std: : list< T > &list. Ref ) { if ( list. Ref. empty() ) cout << "List is empty"; 123 124 125 126 else { std: : ostream_iterator< T > output( cout, " " ); std: : copy( list. Ref. begin(), list. Ref. end(), output ); 127 128 } // end else Outline fig 21_17. cpp (5 of 5) 129 130 } // end function print. List 2003 Prentice Hall, Inc. All rights reserved. 39

values contains: 2 1 4 3 values after sorting contains: 1 2 3 4 After insert, other. Values contains: 2 6 4 8 After splice, values contains: 1 2 3 4 2 6 4 8 After sort, values contains: 1 2 2 3 4 4 6 8 After insert, other. Values contains: 2 4 6 8 After merge: values contains: 1 2 2 2 3 4 4 4 6 6 8 8 other. Values contains: List is empty After pop_front and pop_back: values contains: 2 2 2 3 4 4 4 6 6 8 After unique, values contains: 2 3 4 6 8 After swap: values contains: List is empty other. Values contains: 2 3 4 6 8 After assign, values contains: 2 3 4 6 8 After merge, values contains: 2 2 3 3 4 4 6 6 8 8 After remove( 4 ), values contains: 2 2 3 3 6 6 8 8 Outline fig 21_17. cpp output (1 of 1) 2003 Prentice Hall, Inc. All rights reserved. 40

41 21. 2. 3 deque Sequence Container • deque ("deek"): double-ended queue – – Header <deque> Indexed access using [] Efficient insertion/deletion in front and back Non-contiguous memory: has "smarter" iterators • Same basic operations as vector – Also has • push_front (insert at front of deque) • pop_front (delete from front) 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 18: fig 21_18. cpp // Standard library class deque test program. #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 9 #include <deque> #include <algorithm> 10 11 12 13 14 int main() { std: : deque< double > values; std: : ostream_iterator< double > output( cout, " " ); Outline fig 21_18. cpp (1 of 2) // deque class-template definition // copy algorithm Create a deque, use member functions. 15 16 17 18 19 // insert elements in values. push_front( 2. 2 ); values. push_front( 3. 5 ); values. push_back( 1. 1 ); 20 21 cout << "values contains: "; 22 23 24 25 // use subscript operator to obtain elements of values for ( int i = 0; i < values. size(); ++i ) cout << values[ i ] << ' '; 26 2003 Prentice Hall, Inc. All rights reserved. 42

27 values. pop_front(); 28 29 30 cout << "n. After pop_front, values contains: " ; std: : copy( values. begin(), values. end(), output ); 31 32 33 // use subscript operator to modify element at location 1 values[ 1 ] = 5. 4; 34 35 36 37 38 39 40 41 42 // remove first element cout << "n. After values[ 1 ] = 5. 4, values contains: " ; std: : copy( values. begin(), values. end(), output ); Outline fig 21_18. cpp (2 of 2) fig 21_18. cpp output (1 of 1) cout << endl; return 0; } // end main values contains: 3. 5 2. 2 1. 1 After pop_front, values contains: 2. 2 1. 1 After values[ 1 ] = 5. 4, values contains: 2. 2 5. 4 2003 Prentice Hall, Inc. All rights reserved. 43

44 21. 3 Associative Containers • Associative containers – Direct access to store/retrieve elements – Uses keys (search keys) – 4 types: multiset, multimap and map • Keys in sorted order • multiset and multimap allow duplicate keys • multimap and map have keys and associated values • multiset and set only have values 2003 Prentice Hall, Inc. All rights reserved.

45 Function Object (Functor) Functors are objects that can be treated as though they are a function or function pointer e. g. my. Functor. Class functor; functor( 1, 2, 3 ); This code works because C++ allows you to overload operator(), the "function call" operator. class my. Functor. Class { public: my. Functor. Class (int x) : _x( x ) {} int operator() (int y) { return _x + y; } private: int _x; }; int main() { my. Functor. Class add. Five( 5 ); std: : cout << add. Five( 6 ); return 0; } 2003 Prentice Hall, Inc. All rights reserved.

46 21. 3. 1 multiset Associative Container • multiset – – Header <set> Fast storage, retrieval of keys (no values) Allows duplicates Bidirectional iterators • Ordering of elements – Done by comparator function object • Used when creating multiset – For integer multiset • less<int> comparator function object (functor) • multiset< int, std: : less<int> > my. Object; • Elements will be sorted in ascending order 2003 Prentice Hall, Inc. All rights reserved.

47 21. 3. 1 multiset Associative Container • Multiset functions – ms. insert(value) • Inserts value into multiset – ms. count(value) • Returns number of occurrences of value – ms. find(value) • Returns iterator to first instance of value – ms. lower_bound(value) • Returns iterator to first location of value – ms. upper_bound(value) • Returns iterator to location after last occurrence of value 2003 Prentice Hall, Inc. All rights reserved.

48 21. 3. 1 multiset Associative Container • Class pair – Manipulate pairs of values – pair objects contain first and second • const_iterators – For a pair object q q = ms. equal_range(value) • Sets first and second to lower_bound and upper_bound for a given value 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 19: fig 21_19. cpp // Testing Standard Library class multiset #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 #include <set> 9 10 11 // define short name for multiset type used in this typedef std: : multiset< int, std: : less< int > > ims; 12 13 #include <algorithm> 14 15 16 17 18 int main() { const int SIZE = 10; int a[ SIZE ] = { 7, 22, 9, 1, 18, 30, 100, 22, 85, 13 }; 19 20 21 22 23 24 25 Outline fig 21_19. cpp (1 of 3) typedefs help clarify program. This declares an integer multiset that stores program values in ascending order. // multiset class-template definition // copy algorithm ims int. Multiset; // ims is typedef for "integer multiset" std: : ostream_iterator< int > output( cout, " " ); cout << "There are currently " << int. Multiset. count( 15 ) << " values of 15 in the multisetn" ; 2003 Prentice Hall, Inc. All rights reserved. 49

26 27 int. Multiset. insert( 15 ); 28 29 30 31 cout << "After inserts, there are " << int. Multiset. count( 15 ) << " values of 15 in the multisetnn" ; 32 33 34 // iterator that cannot be used to change element values Use member function ims: : const_iterator result; 35 36 37 // find 15 in int. Multiset; find returns iterator result = int. Multiset. find( 15 ); // insert 15 in int. Multiset 38 39 40 41 42 43 // find 20 in int. Multiset; find returns iterator result = int. Multiset. find( 20 ); 44 45 46 if ( result == int. Multiset. end() ) // will be true hence cout << "Did not find value 20n" ; // did not find 20 47 48 49 // insert elements of array a into int. Multiset. insert( a, a + SIZE ); 50 51 52 cout << "n. After insert, int. Multiset contains: n" ; std: : copy( int. Multiset. begin(), int. Multiset. end(), output ); Outline fig 21_19. cpp (2 of 3) find. if ( result != int. Multiset. end() ) // if iterator not at end cout << "Found value 15n"; // found search value 15 53 2003 Prentice Hall, Inc. All rights reserved. 50

54 55 56 57 58 // determine lower and upper bound of 22 in int. Multiset cout << "nn. Lower bound of 22: " << *( int. Multiset. lower_bound( 22 ) ); cout << "n. Upper bound of 22: " << *( int. Multiset. upper_bound( 22 ) ); 59 60 61 // p represents pair of const_iterators std: : pair< ims: : const_iterator, ims: : const_iterator > p; 62 63 64 65 // use equal_range to determine lower and // of 22 in int. Multiset p = int. Multiset. equal_range( 22 ); 66 67 68 69 cout << "nnequal_range of 22: " << "n Lower bound: " << *( p. first ) << "n Upper bound: " << *( p. second ); 70 71 cout << endl; 72 73 return 0; 74 75 Outline fig 21_19. cpp (3 of 3) Use a pair object to get the upperlower boundand upper bound for 22. } // end main 2003 Prentice Hall, Inc. All rights reserved. 51

There are currently 0 values of 15 in the multiset After inserts, there are 2 values of 15 in the multiset Found value 15 Did not find value 20 After insert, int. Multiset contains: 1 7 9 13 15 15 18 22 22 30 85 100 Outline fig 21_19. cpp output (1 of 1) Lower bound of 22: 22 Upper bound of 22: 30 equal_range of 22: Lower bound: 22 Upper bound: 30 2003 Prentice Hall, Inc. All rights reserved. 52

53 21. 3. 2 set Associative Container • set – Header <set> – Implementation identical to multiset – Unique keys • Duplicates ignored and not inserted – Supports bidirectional iterators (but not random access) – std: : set< type, std: : less<type> > name; 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 20: fig 21_20. cpp // Standard library class set test program. #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 #include <set> 9 10 11 // define short name for set type used in this program typedef std: : set< double, std: : less< double > > double_set; 12 13 #include <algorithm> 14 15 16 17 18 int main() { const int SIZE = 5; double a[ SIZE ] = { 2. 1, 4. 2, 9. 5, 2. 1, 3. 7 }; Outline fig 21_20. cpp (1 of 3) Create set. Syntax similar to multiset. 19 20 21 double_set double. Set( a, a + SIZE ); std: : ostream_iterator< double > output( cout, " " ); 22 23 24 cout << "double. Set contains: "; std: : copy( double. Set. begin(), double. Set. end(), output ); 25 2003 Prentice Hall, Inc. All rights reserved. 54

26 27 // p represents pair containing const_iterator and bool std: : pair< double_set: : const_iterator, bool > p; 28 29 30 31 32 // insert 13. 8 in double. Set; insert returns pair in which // p. first represents location of 13. 8 in double. Set and // p. second represents whether 13. 8 was inserted pair object has a value representing p = double. Set. insert( 13. 8 ); // value not in set 33 34 35 cout << "nn" << *( p. first ) << ( p. second ? " was" : " was not" ) << " inserted"; 36 37 38 cout << "ndouble. Set contains: " ; std: : copy( double. Set. begin(), double. Set. end(), output ); 39 40 41 // insert 9. 5 in double. Set p = double. Set. insert( 9. 5 ); 42 43 44 45 Outline fig 21_20. cpp bool (2 of 3) whether or not the item was inserted. // value already in set cout << "nn" << *( p. first ) << ( p. second ? " was" : " was not" ) << " inserted"; 2003 Prentice Hall, Inc. All rights reserved. 55

46 47 cout << "ndouble. Set contains: " ; std: : copy( double. Set. begin(), double. Set. end(), output ); 48 49 cout << endl; 50 51 return 0; 52 53 } // end main Outline fig 21_20. cpp (3 of 3) fig 21_20. cpp output (1 of 1) double. Set contains: 2. 1 3. 7 4. 2 9. 5 13. 8 was inserted double. Set contains: 2. 1 3. 7 4. 2 9. 5 13. 8 9. 5 was not inserted double. Set contains: 2. 1 3. 7 4. 2 9. 5 13. 8 2003 Prentice Hall, Inc. All rights reserved. 56

57 21. 3. 3 multimap Associative Container • multimap – Header <map> – Fast storage and retrieval of keys and associated values • Has key/value pairs – Duplicate keys allowed (multiple values for a single key) • One-to-many relationship • I. e. , one student can take many courses – Insert pair objects (with a key and value) – Bidirectional iterators 2003 Prentice Hall, Inc. All rights reserved.

58 21. 3. 3 multimap Associative Container • Example std: : multimap< int, double, std: : less< int > > mmap. Object; – Key type int – Value type double – Sorted in ascending order • Use typedef to simplify code typedef std: : multimap<int, double, std: : less<int>> mmid; mmid mmap. Object; mmap. Object. insert( mmid: : value_type( 1, 3. 4 ) ); – Inserts key 1 with value 3. 4 – mmid: : value_type creates a pair object 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21: fig 21_21. cpp // Standard library class multimap test program. #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 #include <map> 9 10 11 // define short name for multimap type used in this program typedef std: : multimap< int, double, std: : less< int > > mmid; 12 13 14 15 int main() { mmid pairs; 16 17 18 19 20 21 22 23 24 25 26 // map class-template definition Outline fig 21_21. cpp Definition for a multimap (1 of 2) that maps integer keys to double values. Create multimap and insert key-value pairs. cout << "There are currently " << pairs. count( 15 ) << " pairs with key 15 in the multimapn" ; // insert two value_type objects in pairs. insert( mmid: : value_type( 15, 2. 7 ) ); pairs. insert( mmid: : value_type( 15, 99. 3 ) ); cout << "After inserts, there are " << pairs. count( 15 ) << " pairs with key 15nn" ; 2003 Prentice Hall, Inc. All rights reserved. 59

27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 Use iterator; to cout << "Multimap pairs contains: n. Keyt. Valuen" fig 21_21. cpp (2 of 2) print entire multimap. // use const_iterator to walk through elements of pairs for ( mmid: : const_iterator iter = pairs. begin(); iter != pairs. end(); ++iter ) cout << iter->first << 't' << iter->second << 'n'; 42 43 cout << endl; 44 45 return 0; 46 47 Outline // insert five value_type objects in pairs. insert( mmid: : value_type( 30, 111. 11 ) ); pairs. insert( mmid: : value_type( 10, 22. 22 ) ); pairs. insert( mmid: : value_type( 25, 33. 333 ) ); pairs. insert( mmid: : value_type( 20, 9. 345 ) ); pairs. insert( mmid: : value_type( 5, 77. 54 ) ); } // end main 2003 Prentice Hall, Inc. All rights reserved. 60

There are currently 0 pairs with key 15 in the multimap After inserts, there are 2 pairs with key 15 Multimap pairs contains: Key Value 5 77. 54 10 22. 22 15 2. 7 15 99. 3 20 9. 345 25 33. 333 30 111. 11 Outline fig 21_21. cpp output (1 of 1) 2003 Prentice Hall, Inc. All rights reserved. 61

62 21. 3. 4 map Associative Container • map – Header <map> – Like multimap, but only unique key/value pairs • One-to-one mapping (duplicates ignored) – Use [] to access values – Example: for map object m m[30] = 4000. 21; • Sets the value of key 30 to 4000. 21 – If subscript not in map, creates new key/value pair • Type declaration – std: : map< int, double, std: : less< int > >; 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 22: fig 21_22. cpp // Standard library class map test program. #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 #include <map> 9 10 11 // define short name for map type used in this program typedef std: : map< int, double, std: : less< int > > mid; 12 13 14 15 int main() { mid pairs; 16 17 18 19 20 21 22 23 24 25 Outline fig 21_22. cpp (1 of 2) Again, use typedefs to simplify declaration. // map class-template definition // insert eight value_type objects in pairs. insert( mid: : value_type( 15, 2. 7 ) ); pairs. insert( mid: : value_type( 30, 111. 11 ) ); pairs. insert( mid: : value_type( 5, 1010. 1 ) ); pairs. insert( mid: : value_type( 10, 22. 22 ) ); pairs. insert( mid: : value_type( 25, 33. 333 ) ); pairs. insert( mid: : value_type( 5, 77. 54 ) ); // dupe ignored pairs. insert( mid: : value_type( 20, 9. 345 ) ); pairs. insert( mid: : value_type( 15, 99. 3 ) ); // dupe ignored Duplicate keys ignored. 26 2003 Prentice Hall, Inc. All rights reserved. 63

27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 cout << "pairs contains: n. Keyt. Valuen" ; // use const_iterator to walk through elements of pairs for ( mid: : const_iterator iter = pairs. begin(); iter != pairs. end(); ++iter ) cout << iter->first << 't' Can use subscript << iter->second << 'n'; fig 21_22. cpp (2 of 2) operator to add or change key-value pairs. // use subscript operator to change value for key 25 pairs[ 25 ] = 9999. 99; // use subscript operator insert value for key 40 pairs[ 40 ] = 8765. 43; cout << "n. After subscript operations, pairs contains: " << "n. Keyt. Valuen"; for ( mid: : const_iterator iter 2 = pairs. begin(); iter 2 != pairs. end(); ++iter 2 ) cout << iter 2 ->first << 't' << iter 2 ->second << 'n'; 48 49 cout << endl; 50 51 return 0; 52 53 Outline } // end main 2003 Prentice Hall, Inc. All rights reserved. 64

pairs contains: Key Value 5 1010. 1 10 22. 22 15 2. 7 20 9. 345 25 33. 333 30 111. 11 Outline fig 21_22. cpp output (1 of 1) After subscript operations, pairs contains: Key Value 5 1010. 1 10 22. 22 15 2. 7 20 9. 345 25 9999. 99 30 111. 11 40 8765. 43 2003 Prentice Hall, Inc. All rights reserved. 65

66 21. 4 Container Adapters • Container adapters – stack, queue and priority_queue – Not first class containers • Do not support iterators • Do not provide actual data structure – Programmer can select implementation – Member functions push and pop 2003 Prentice Hall, Inc. All rights reserved.

67 21. 4. 1 stack Adapter • stack – – – Header <stack> Insertions and deletions at one end Last-in, first-out (LIFO) data structure Can use vector, list, or deque (default) Declarations stack<type, vector<type> > my. Stack; stack<type, list<type> > my. Other. Stack; stack<type> another. Stack; // default deque • vector, list – Implementation of stack (default deque) – Does not change behavior, just performance (deque and vector fastest) 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 23: fig 21_23. cpp // Standard library adapter stack test program. #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 9 10 #include <stack> #include <vector> #include <list> 11 12 13 14 // pop. Elements function-template prototype template< class T > void pop. Elements( T &stack. Ref ); 15 16 17 18 19 int main() { // stack with default underlying deque std: : stack< int > int. Deque. Stack; Outline fig 21_23. cpp (1 of 3) // stack adapter definition // vector class-template definition // list class-template definition Create stacks with various implementations. 20 21 22 // stack with underlying vector std: : stack< int, std: : vector< int > > int. Vector. Stack; 23 24 25 // stack with underlying list std: : stack< int, std: : list< int > > int. List. Stack; 26 2003 Prentice Hall, Inc. All rights reserved. 68

27 28 29 30 31 // push the values 0 -9 onto each stack for ( int i = 0; i < 10; ++i ) { int. Deque. Stack. push( i ); int. Vector. Stack. push( i ); int. List. Stack. push( i ); 32 33 } // end for 34 35 36 37 38 39 40 41 // display and remove elements from each stack cout << "Popping from int. Deque. Stack: " ; pop. Elements( int. Deque. Stack ); cout << "n. Popping from int. Vector. Stack: " ; pop. Elements( int. Vector. Stack ); cout << "n. Popping from int. List. Stack: " ; pop. Elements( int. List. Stack ); 42 43 cout << endl; 44 45 return 0; 46 47 Outline Use member function push. fig 21_23. cpp (2 of 3) } // end main 48 2003 Prentice Hall, Inc. All rights reserved. 69

49 50 51 52 53 54 55 56 57 58 59 // pop elements from stack object to which stack. Ref refers template< class T > void pop. Elements( T &stack. Ref ) { while ( !stack. Ref. empty() ) { cout << stack. Ref. top() << ' '; // view top element stack. Ref. pop(); // remove top element } // end while Outline fig 21_23. cpp (3 of 3) fig 21_23. cpp output (1 of 1) } // end function pop. Elements Popping from int. Deque. Stack: 9 8 7 6 5 4 3 2 1 0 Popping from int. Vector. Stack: 9 8 7 6 5 4 3 2 1 0 Popping from int. List. Stack: 9 8 7 6 5 4 3 2 1 0 2003 Prentice Hall, Inc. All rights reserved. 70

71 21. 4. 2 queue Adapter • queue – – Header <queue> Insertions at back, deletions at front First-in-first-out (FIFO) data structure Implemented with list or deque (default) • std: : queue<double> values; • Functions – push( element ) • Same as push_back, add to end – pop( element ) • Implemented with pop_front, remove from front – empty() – size() 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 24: fig 21_24. cpp // Standard library adapter queue test program. #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 #include <queue> 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Outline fig 21_24. cpp (1 of 2) // queue adapter definition int main() { std: : queue< double > values; // push elements values. push( 3. 2 values. push( 9. 8 values. push( 5. 4 Create queue, add values using push. onto queue values ); ); ); cout << "Popping from values: "; while ( !values. empty() ) { cout << values. front() << ' '; values. pop(); // view front element // remove element } // end while 26 2003 Prentice Hall, Inc. All rights reserved. 72

27 cout << endl; 28 29 return 0; 30 31 } // end main Popping from values: 3. 2 9. 8 5. 4 Outline fig 21_24. cpp (2 of 2) fig 21_24. cpp output (1 of 1) 2003 Prentice Hall, Inc. All rights reserved. 73

74 21. 4. 3 priority_queue Adapter • priority_queue – – Header <queue> Insertions happen in sorted order, deletions from front Implemented with vector (default) or deque Highest priority element always removed first • Heapsort algorithm puts largest elements at front • less<T> default, programmer can specify other comparator – Functions • push(value), pop(value) • top() – View top element • size() • empty() 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 25: fig 21_25. cpp // Standard library adapter priority_queue test program. #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 #include <queue> 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Outline fig 21_25. cpp (1 of 2) // priority_queue adapter definition Create priority queue. int main() { std: : priority_queue< double > priorities; // push elements priorities. push( onto priorities 3. 2 ); 9. 8 ); 5. 4 ); Insert items using push. When using pop, highest priority (largest) items removed first. cout << "Popping from priorities: " ; while ( !priorities. empty() ) { cout << priorities. top() << ' '; priorities. pop(); // view top element // remove top element } // end while 26 2003 Prentice Hall, Inc. All rights reserved. 75

27 cout << endl; 28 29 return 0; 30 31 } // end main Popping from priorities: 9. 8 5. 4 3. 2 Outline fig 21_25. cpp (2 of 2) fig 21_25. cpp output (1 of 1) 2003 Prentice Hall, Inc. All rights reserved. 76

77 21. 5 Algorithms • Before STL – Class libraries incompatible among vendors – Algorithms built into container classes • STL separates containers and algorithms – Easier to add new algorithms – More efficient, avoids virtual function calls – <algorithm> 2003 Prentice Hall, Inc. All rights reserved.

78 21. 5. 1 fill, fill_n, generate and generate_n • Functions to change containers – fill(iterator 1, iterator 2, value); • Sets range of elements to value – fill_n(iterator 1, n, value); • Sets n elements to value, starting at iterator 1 – generate(iterator 1, iterator 2, function); • Like fill, but calls function to set each value – generate(iterator 1, quantity, function) • Like fill_n, "" 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 4 // Fig. 21. 26: fig 21_26. cpp // Standard library algorithms fill, fill_n, generate // and generate_n. #include <iostream> 5 6 7 using std: : cout; using std: : endl; 8 9 10 #include <algorithm> #include <vector> // algorithm definitions // vector class-template definition 11 12 char next. Letter(); // prototype 13 14 15 16 17 int main() { std: : vector< char > chars( 10 ); std: : ostream_iterator< char > output( cout, " " ); Outline fig 21_26. cpp (1 of 3) Create vector of chars, to be used with various functions. 18 19 20 // fill chars with 5 s std: : fill( chars. begin(), chars. end(), '5' ); 21 22 23 cout << "Vector chars after filling with 5 s: n" ; std: : copy( chars. begin(), chars. end(), output ); Function fill. 24 2003 Prentice Hall, Inc. All rights reserved. 79

25 26 // fill first five elements of chars with As std: : fill_n( chars. begin(), 5, 'A' ); 27 28 29 30 cout << "nn. Vector chars after filling five elements" << " with As: n"; std: : copy( chars. begin(), chars. end(), output ); 31 32 33 // generate values for all elements of chars with next. Letter std: : generate( chars. begin(), chars. end(), next. Letter ); 34 35 36 cout << "nn. Vector chars after generating letters A-J: n" ; std: : copy( chars. begin(), chars. end(), output ); 37 38 39 40 // generate values for first five elements of chars // with next. Letter std: : generate_n( chars. begin(), 5, next. Letter ); 41 42 43 44 cout << "nn. Vector chars after generating K-O for the" << " first five elements: n" ; std: : copy( chars. begin(), chars. end(), output ); 45 46 cout << endl; 47 48 return 0; 49 50 Outline fig 21_26. cpp Functions generate and (2 of 3) generate_n use function next. Letter. } // end main 2003 Prentice Hall, Inc. All rights reserved. 80

51 52 53 54 55 56 // returns next letter in the alphabet (starts with A) char next. Letter() { static char letter = 'A'; return letter++; 57 58 } // end function next. Letter Outline fig 21_26. cpp (3 of 3) fig 21_26. cpp output (1 of 1) Vector chars after filling with 5 s: 5 5 5 5 5 Vector chars after filling five elements with As: A A A 5 5 5 Vector chars after generating letters A-J: A B C D E F G H I J Vector chars after generating K-O for the first five elements: K L M N O F G H I J 2003 Prentice Hall, Inc. All rights reserved. 81

21. 5. 2 equal, mismatch and lexicographical_compare • Functions to compare sequences of values – equal • Returns true if sequences are equal (uses ==) • Can return false if of unequal length equal(iterator 1, iterator 2, iterator 3); • Compares sequence from iterator 1 to iterator 2 with sequence beginning at iterator 3 – mismatch • Arguments same as equal • Returns a pair object with iterators pointing to mismatch – If no mismatch, pair iterators equal to last item pair < iterator, iterator > my. Pair. Object; my. Pair. Object = mismatch( iter 1, iter 2, iter 3); 2003 Prentice Hall, Inc. All rights reserved. 82

21. 5. 2 equal, mismatch and lexicographical_compare • Functions to compare sequences of values – lexicographical_compare • Compare contents of two character arrays • Returns true if element in first sequence smaller than corresponding element in second bool result = lexicographical_compare(iter 1, iter 2, iter 3); 2003 Prentice Hall, Inc. All rights reserved. 83

1 2 3 4 // Fig. 21. 27: fig 21_27. cpp // Standard library functions equal, // mismatch and lexicographical_compare. #include <iostream> 5 6 7 using std: : cout; using std: : endl; 8 9 10 #include <algorithm> #include <vector> 11 12 13 14 15 16 int main() { const int SIZE = 10; int a 1[ SIZE ] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; int a 2[ SIZE ] = { 1, 2, 3, 4, 1000, 6, 7, 8, 9, 10 }; Outline fig 21_27. cpp (1 of 3) // algorithm definitions // vector class-template definition 17 18 19 20 std: : vector< int > v 1( a 1, a 1 + SIZE ); std: : vector< int > v 2( a 1, a 1 + SIZE ); std: : vector< int > v 3( a 2, a 2 + SIZE ); 21 22 std: : ostream_iterator< int > output( cout, " " ); 23 2003 Prentice Hall, Inc. All rights reserved. 84

24 25 26 27 28 29 cout << "Vector v 1 contains: "; std: : copy( v 1. begin(), v 1. end(), output ); cout << "n. Vector v 2 contains: " ; std: : copy( v 2. begin(), v 2. end(), output ); cout << "n. Vector v 3 contains: " ; std: : copy( v 3. begin(), v 3. end(), output ); 30 31 32 33 // compare vectors v 1 and v 2 for equality bool result = std: : equal( v 1. begin(), v 1. end(), v 2. begin() ); 34 35 36 cout << "nn. Vector v 1 " << ( result ? "is" : "is not" ) << " equal to vector v 2. n" ; 37 38 39 40 41 // compare vectors v 1 and v 3 for equality result = std: : equal( v 1. begin(), v 1. end(), v 3. begin() ); cout << "Vector v 1 " << ( result ? "is" : "is not" ) << " equal to vector v 3. n" ; 42 43 44 45 // location represents pair of vector iterators std: : pair< std: : vector< int >: : iterator, std: : vector< int >: : iterator > location; 46 47 48 49 // check for mismatch between v 1 and v 3 location = std: : mismatch( v 1. begin(), v 1. end(), v 3. begin() ); Outline fig 21_27. cpp (2 of 3) Use function equal. Compares all of v 1 with v 2. Note use of function mismatch. 50 2003 Prentice Hall, Inc. All rights reserved. 85

51 52 53 54 55 cout << << << 56 57 58 char c 1[ SIZE ] = "HELLO"; char c 2[ SIZE ] = "BYE BYE"; 59 60 61 62 // perform lexicographical comparison of c 1 and c 2 result = std: : lexicographical_compare( c 1, c 1 + SIZE, c 2 + SIZE ); 63 64 65 66 67 cout << c 1 << ( result ? " is less than " : " is greater than or equal to " ) << c 2 << endl; 68 69 return 0; 70 71 "n. There is a mismatch between v 1 and v 3 at " "location " << ( location. first - v 1. begin() ) "nwhere v 1 contains " << *location. first " and v 3 contains " << *location. second "nn"; Outline fig 21_27. cpp (3 of 3) Use lexicographical_compare. } // end main 2003 Prentice Hall, Inc. All rights reserved. 86

Vector v 1 contains: 1 2 3 4 5 6 7 8 9 10 Vector v 2 contains: 1 2 3 4 5 6 7 8 9 10 Vector v 3 contains: 1 2 3 4 1000 6 7 8 9 10 Vector v 1 is equal to vector v 2. Vector v 1 is not equal to vector v 3. Outline fig 21_27. cpp output (1 of 1) There is a mismatch between v 1 and v 3 at location 4 where v 1 contains 5 and v 3 contains 1000 HELLO is greater than or equal to BYE 2003 Prentice Hall, Inc. All rights reserved. 87

21. 5. 3 remove, remove_if, remove_copy and remove_copy_if • remove – remove( iter 1, iter 2, value); – Removes all instances of value in range (iter 1 -iter 2) • Moves instances of value towards end • Does not change size of container or delete elements – Returns iterator to "new" end of container – Elements after new iterator are undefined (0) • remove_copy – Copies one vector to another while removing an element – remove_copy(iter 1, iter 2, iter 3, value); • Copies elements not equal to value into iter 3 (output iterator) • Uses range iter 1 -iter 2 2003 Prentice Hall, Inc. All rights reserved. 88

21. 5. 3 remove, remove_if, remove_copy and remove_copy_if • remove_if – Like remove • Returns iterator to last element • Removes elements that return true for specified function remove_if(iter 1, iter 2, function); • Elements passed to function, which returns a bool • remove_copy_if – Like remove_copy and remove_if – Copies range of elements to iter 3, except those for which function returns true remove_copy_if(iter 1, iter 2, iter 3, function); 2003 Prentice Hall, Inc. All rights reserved. 89

1 2 3 4 // Fig. 21. 28: fig 21_28. cpp // Standard library functions remove, remove_if, // remove_copy and remove_copy_if. #include <iostream> 5 6 7 using std: : cout; using std: : endl; 8 9 10 #include <algorithm> #include <vector> // algorithm definitions // vector class-template definition 11 12 bool greater 9( int ); // prototype 13 14 15 16 17 int main() { const int SIZE = 10; int a[ SIZE ] = { 10, 2, 10, 4, 16, 6, 14, 8, 12, 10 }; 18 19 20 21 22 23 24 25 Outline fig 21_28. cpp (1 of 4) std: : ostream_iterator< int > output( cout, " " ); std: : vector< int > v( a, a + SIZE ); std: : vector< int >: : iterator new. Last. Element; cout << "Vector v before removing all 10 s: n std: : copy( v. begin(), v. end(), output ); "; 26 2003 Prentice Hall, Inc. All rights reserved. 90

27 28 // remove 10 from v new. Last. Element = std: : remove( v. begin(), v. end(), 10 ); 29 30 31 cout << "n. Vector v after removing all 10 s: n "; std: : copy( v. begin(), new. Last. Element, output ); 32 33 34 std: : vector< int > v 2( a, a + SIZE ); std: : vector< int > c( SIZE, 0 ); 35 36 37 38 cout << "nn. Vector v 2 before removing all 10 s " << "and copying: n "; std: : copy( v 2. begin(), v 2. end(), output ); 39 40 41 // copy from v 2 to c, removing 10 s in the process std: : remove_copy( v 2. begin(), v 2. end(), c. begin(), 10 ); 42 43 44 cout << "n. Vector c after removing all 10 s from v 2: n std: : copy( c. begin(), c. end(), output ); 45 46 std: : vector< int > v 3( a, a + SIZE ); 47 48 49 50 cout << "nn. Vector v 3 before removing all elements" << "ngreater than 9: n "; std: : copy( v 3. begin(), v 3. end(), output ); Outline Remove all 10's from v. fig 21_28. cpp Returns an iterator pointing to (2 of 4) the new last element. Use remove_copy to create a duplicate of v, with all the 10's removed. "; 51 2003 Prentice Hall, Inc. All rights reserved. 91

52 53 54 // remove elements greater than 9 from v 3 new. Last. Element = std: : remove_if( v 3. begin(), v 3. end(), greater 9 ); 55 56 57 58 cout << "n. Vector v 3 after removing all elements" << "ngreater than 9: n "; std: : copy( v 3. begin(), new. Last. Element, output ); 59 60 61 std: : vector< int > v 4( a, a + SIZE ); std: : vector< int > c 2( SIZE, 0 ); 62 63 64 65 66 67 68 69 70 71 72 73 74 Outline fig 21_28. cpp Use function greater 9 to (3 of 4) determine whether to remove the element. cout << "nn. Vector v 4 before removing all elements" << "ngreater than 9 and copying: n "; std: : copy( v 4. begin(), v 4. end(), output ); Note use of remove_copy_if. // copy elements from v 4 to c 2, removing elements greater // than 9 in the process std: : remove_copy_if( v 4. begin(), v 4. end(), c 2. begin(), greater 9 ); cout << "n. Vector c 2 after removing all elements" << "ngreater than 9 from v 4: n "; std: : copy( c 2. begin(), c 2. end(), output ); 75 2003 Prentice Hall, Inc. All rights reserved. 92

76 cout << endl; 77 78 return 0; 79 80 } // end main 81 82 83 84 85 // determine whether argument is greater than 9 bool greater 9( int x ) { return x > 9; 86 87 } // end greater 9 Outline fig 21_28. cpp (4 of 4) 2003 Prentice Hall, Inc. All rights reserved. 93

Vector v before removing all 10 s: 10 2 10 4 16 6 14 8 12 10 Vector v after removing all 10 s: 2 4 16 6 14 8 12 Vector v 2 before removing all 10 s and copying: 10 2 10 4 16 6 14 8 12 10 Vector c after removing all 10 s from v 2: 2 4 16 6 14 8 12 0 0 0 Outline fig 21_28. cpp output (1 of 1) Vector v 3 before removing all elements greater than 9: 10 2 10 4 16 6 14 8 12 10 Vector v 3 after removing all elements greater than 9: 2 4 6 8 Vector v 4 before removing all elements greater than 9 and copying: 10 2 10 4 16 6 14 8 12 10 Vector c 2 after removing all elements greater than 9 from v 4: 2 4 6 8 0 0 0 2003 Prentice Hall, Inc. All rights reserved. 94

21. 5. 4 replace, replace_if, replace_copy and replace_copy_if • Functions – replace( iter 1, iter 2, value, newvalue ); • Like remove, except replaces value with newvalue – replace_if( iter 1, iter 2, function, newvalue ); • Replaces value if function returns true – replace_copy(iter 1, iter 2, iter 3, value, newvalue); • Replaces and copies elements to iter 3 • Does not affect originals – replace_copy_if( iter 1, iter 2, iter 3, function, newvalue ); • Replaces and copies elements to iter 3 if function returns true 2003 Prentice Hall, Inc. All rights reserved. 95

1 2 3 4 // Fig. 21. 29: fig 21_29. cpp // Standard library functions replace, replace_if, // replace_copy and replace_copy_if. #include <iostream> 5 6 7 using std: : cout; using std: : endl; 8 9 10 #include <algorithm> #include <vector> 11 12 bool greater 9( int ); 13 14 15 16 17 int main() { const int SIZE = 10; int a[ SIZE ] = { 10, 2, 10, 4, 16, 6, 14, 8, 12, 10 }; Outline fig 21_29. cpp (1 of 4) 18 19 std: : ostream_iterator< int > output( cout, " " ); 20 21 22 23 std: : vector< int > v 1( a, a + SIZE ); cout << "Vector v 1 before replacing all 10 s: n std: : copy( v 1. begin(), v 1. end(), output ); "; 24 2003 Prentice Hall, Inc. All rights reserved. 96

25 26 // replace 10 s in v 1 with 100 std: : replace( v 1. begin(), v 1. end(), 100 ); 27 28 29 cout << "n. Vector v 1 after replacing 10 s with 100 s: n std: : copy( v 1. begin(), v 1. end(), output ); 30 31 32 std: : vector< int > v 2( a, a + SIZE ); std: : vector< int > c 1( SIZE ); 33 34 35 36 cout << "nn. Vector v 2 before replacing all 10 s " << "and copying: n "; std: : copy( v 2. begin(), v 2. end(), output ); 37 38 39 40 // copy from v 2 to c 1, replacing 10 s with 100 s std: : replace_copy( v 2. begin(), v 2. end(), c 1. begin(), 100 ); 41 42 43 cout << "n. Vector c 1 after replacing all 10 s in v 2: n std: : copy( c 1. begin(), c 1. end(), output ); 44 45 std: : vector< int > v 3( a, a + SIZE ); 46 47 48 49 cout << "nn. Vector v 3 before replacing values greater" << " than 9: n "; std: : copy( v 3. begin(), v 3. end(), output ); Outline Use functions replace, replace_copy. "; fig 21_29. cpp (2 of 4) "; 50 2003 Prentice Hall, Inc. All rights reserved. 97

51 52 // replace values greater than 9 in v 3 with 100 std: : replace_if( v 3. begin(), v 3. end(), greater 9, 100 ); 53 54 55 56 cout << "n. Vector v 3 after replacing all values greater" << "nthan 9 with 100 s: n "; std: : copy( v 3. begin(), v 3. end(), output ); 57 58 59 std: : vector< int > v 4( a, a + SIZE ); std: : vector< int > c 2( SIZE ); 60 61 62 63 cout << "nn. Vector v 4 before replacing all values greater " << "than 9 and copying: n "; std: : copy( v 4. begin(), v 4. end(), output ); 64 65 66 67 // copy v 4 to c 2, replacing elements greater than 9 with 100 std: : replace_copy_if( v 4. begin(), v 4. end(), c 2. begin(), greater 9, 100 ); 68 69 70 71 cout << "n. Vector c 2 after replacing all values greater " << "than 9 in v 4: n "; std: : copy( c 2. begin(), c 2. end(), output ); 72 73 cout << endl; 74 75 return 0; 76 77 Outline fig 21_29. cpp (3 of 4) } // end main 2003 Prentice Hall, Inc. All rights reserved. 98

78 79 80 81 82 // determine whether argument is greater than 9 bool greater 9( int x ) { return x > 9; 83 84 } // end function greater 9 Vector v 1 before replacing all 10 s: 10 2 10 4 16 6 14 8 12 10 Vector v 1 after replacing 10 s with 100 s: 100 2 100 4 16 6 14 8 12 100 Outline fig 21_29. cpp (4 of 4) fig 21_29. cpp output (1 of 1) Vector v 2 before replacing all 10 s and copying: 10 2 10 4 16 6 14 8 12 10 Vector c 1 after replacing all 10 s in v 2: 100 2 100 4 16 6 14 8 12 100 Vector v 3 before replacing values greater than 9: 10 2 10 4 16 6 14 8 12 10 Vector v 3 after replacing all values greater than 9 with 100 s: 100 2 100 4 100 6 100 8 100 Vector v 4 before replacing all values greater than 9 and copying: 10 2 10 4 16 6 14 8 12 10 Vector c 2 after replacing all values greater than 9 in v 4: 100 2 100 4 100 6 100 8 100 2003 Prentice Hall, Inc. All rights reserved. 99

100 21. 5. 5 Mathematical Algorithms • random_shuffle(iter 1, iter 2) – Randomly mixes elements in range • count(iter 1, iter 2, value) – Returns number of instances of value in range • count_if(iter 1, iter 2, function) – Counts number of instances that return true • min_element(iter 1, iter 2) – Returns iterator to smallest element • max_element(iter 1, iter 2) – Returns iterator to largest element 2003 Prentice Hall, Inc. All rights reserved.

101 21. 5. 5 Mathematical Algorithms • accumulate(iter 1, iter 2) – Returns sum of elements in range • for_each(iter 1, iter 2, function) – Calls function on every element in range – Does not modify element • transform(iter 1, iter 2, iter 3, function) – Calls function for all elements in range of iter 1 -iter 2, copies result to iter 3 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 30: fig 21_30. cpp // Mathematical algorithms of the standard library. #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 9 10 #include <algorithm> #include <numeric> #include <vector> 11 12 13 14 bool greater 9( int ); void output. Square( int ); int calculate. Cube( int ); 15 16 17 18 19 int main() { const int SIZE = 10; int a 1[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; Outline 102 fig 21_30. cpp (1 of 5) // algorithm definitions // accumulate is defined here 20 21 22 std: : vector< int > v( a 1, a 1 + SIZE ); std: : ostream_iterator< int > output( cout, " " ); 23 24 25 cout << "Vector v before random_shuffle: " ; std: : copy( v. begin(), v. end(), output ); 26 2003 Prentice Hall, Inc. All rights reserved.

27 28 // shuffle elements of v std: : random_shuffle( v. begin(), v. end() ); 29 30 31 cout << "n. Vector v after random_shuffle: " ; std: : copy( v. begin(), v. end(), output ); 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 Outline 103 fig 21_30. cpp (2 of 5) int a 2[] = { 100, 2, 8, 1, 50, 3, 8, 8, 9, 10 }; std: : vector< int > v 2( a 2, a 2 + SIZE ); cout << "nn. Vector v 2 contains: " ; std: : copy( v 2. begin(), v 2. end(), output ); // count number of elements in v 2 with value 8 int result = std: : count( v 2. begin(), v 2. end(), 8 ); std: : cout << "n. Number of elements matching 8: " << result; // count number of elements in v 2 that are greater than 9 result = std: : count_if( v 2. begin(), v 2. end(), greater 9 ); cout << "n. Number of elements greater than 9: " << result; 48 2003 Prentice Hall, Inc. All rights reserved.

49 50 51 // locate minimum element in v 2 cout << "nn. Minimum element in Vector v 2 is: " << *( std: : min_element( v 2. begin(), v 2. end() ) ); 52 53 54 55 // locate maximum element in v 2 cout << "n. Maximum element in Vector v 2 is: " << *( std: : max_element( v 2. begin(), v 2. end() ) ); 56 57 58 59 // calculate sum of elements in v cout << "nn. The total of the elements in Vector v is: " << std: : accumulate( v. begin(), v. end(), 0 ); 60 61 cout << "nn. The square of every integer in Vector v is: n" ; 62 63 64 // output square of every element in v std: : for_each( v. begin(), v. end(), output. Square ); 65 66 67 68 69 70 71 Outline 104 fig 21_30. cpp (3 of 5) std: : vector< int > cubes( SIZE ); // calculate cube of each element in v; // place results in cubes std: : transform( v. begin(), v. end(), cubes. begin(), calculate. Cube ); 2003 Prentice Hall, Inc. All rights reserved.

72 73 74 cout << "nn. The cube of every integer in Vector v is: n" ; std: : copy( cubes. begin(), cubes. end(), output ); 75 76 cout << endl; 77 78 return 0; 79 80 } // end main 81 82 83 84 85 // determine whether argument is greater than 9 bool greater 9( int value ) { return value > 9; 86 87 } // end function greater 9 88 89 90 91 92 // output square of argument void output. Square( int value ) { cout << value * value << ' '; 93 94 } // end function output. Square Outline 105 fig 21_30. cpp (4 of 5) 95 2003 Prentice Hall, Inc. All rights reserved.

96 97 98 99 // return cube of argument int calculate. Cube( int value ) { return value * value; 100 101 } // end function calculate. Cube Vector v before random_shuffle: 1 2 3 4 5 6 7 8 9 10 Vector v after random_shuffle: 5 4 1 3 7 8 9 10 6 2 Outline 106 fig 21_30. cpp (5 of 5) fig 21_30. cpp output (1 of 1) Vector v 2 contains: 100 2 8 1 50 3 8 8 9 10 Number of elements matching 8: 3 Number of elements greater than 9: 3 Minimum element in Vector v 2 is: 1 Maximum element in Vector v 2 is: 100 The total of the elements in Vector v is: 55 The square of every integer in Vector v is: 25 16 1 9 49 64 81 100 36 4 The cube of every integer in Vector v is: 125 64 1 27 343 512 729 1000 216 8 2003 Prentice Hall, Inc. All rights reserved.

21. 5. 6 Basic Searching and Sorting Algorithms • find(iter 1, iter 2, value) – Returns iterator to first instance of value (in range) • find_if(iter 1, iter 2, function) – Like find – Returns iterator when function returns true • sort(iter 1, iter 2) – Sorts elements in ascending order • binary_search(iter 1, iter 2, value) – Searches ascending sorted list for value – Uses binary search 2003 Prentice Hall, Inc. All rights reserved. 107

1 2 3 // Fig. 21. 31: fig 21_31. cpp // Standard library search and sort algorithms. #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 9 #include <algorithm> #include <vector> 10 11 bool greater 10( int value ); 12 13 14 15 16 int main() { const int SIZE = 10; int a[ SIZE ] = { 10, 2, 17, 5, 16, 8, 13, 11, 20, 7 }; 17 18 19 20 21 22 23 24 25 26 Outline 108 fig 21_31. cpp (1 of 4) // algorithm definitions // vector class-template definition // prototype std: : vector< int > v( a, a + SIZE ); std: : ostream_iterator< int > output( cout, " " ); cout << "Vector v contains: "; std: : copy( v. begin(), v. end(), output ); // locate first occurrence of 16 in v std: : vector< int >: : iterator location; location = std: : find( v. begin(), v. end(), 16 ); 2003 Prentice Hall, Inc. All rights reserved.

27 28 29 30 31 32 33 34 35 // locate first occurrence of 100 in v location = std: : find( v. begin(), v. end(), 100 ); 36 37 38 39 40 41 if ( location != v. end() ) cout << "n. Found 100 at location " << ( location - v. begin() ); else cout << "n 100 not found"; 42 43 44 // locate first occurrence of value greater than 10 in v location = std: : find_if( v. begin(), v. end(), greater 10 ); 45 46 47 48 49 50 51 if ( location != v. end() ) cout << "nn. The first value greater than 10 is " << *location << "nfound at location " << ( location - v. begin() ); else cout << "nn. No values greater than 10 were found" ; if ( location != v. end() ) cout << "nn. Found 16 at location " << ( location - v. begin() ); else cout << "nn 16 not found"; Outline 109 fig 21_31. cpp (2 of 4) 52 2003 Prentice Hall, Inc. All rights reserved.

53 54 // sort elements of v std: : sort( v. begin(), v. end() ); 55 56 57 cout << "nn. Vector v after sort: " ; std: : copy( v. begin(), v. end(), output ); 58 59 60 61 62 63 // use binary_search to locate 13 in v if ( std: : binary_search( v. begin(), v. end(), 13 ) ) cout << "nn 13 was found in v"; else cout << "nn 13 was not found in v" ; 64 65 66 67 68 69 // use binary_search to locate 100 in v if ( std: : binary_search( v. begin(), v. end(), 100 ) ) cout << "n 100 was found in v"; else cout << "n 100 was not found in v" ; 70 71 cout << endl; 72 73 return 0; 74 75 Outline 110 fig 21_31. cpp (3 of 4) } // end main 76 2003 Prentice Hall, Inc. All rights reserved.

77 78 79 80 // determine whether argument is greater than 10 bool greater 10( int value ) { return value > 10; 81 82 } // end function greater 10 Vector v contains: 10 2 17 5 16 8 13 11 20 7 Found 16 at location 4 100 not found Outline 111 fig 21_31. cpp (4 of 4) fig 21_31. cpp output (1 of 1) The first value greater than 10 is 17 found at location 2 Vector v after sort: 2 5 7 8 10 11 13 16 17 20 13 was found in v 100 was not found in v 2003 Prentice Hall, Inc. All rights reserved.

112 21. 5. 7 swap, iter_swap and swap_ranges • swap(element 1, element 2) – Exchanges two values – swap( a[ 0 ], a[ 1 ] ); • iter_swap(iter 1, iter 2) – Exchanges the values to which the iterators refer • swap_ranges(iter 1, iter 2, iter 3) – Swap the elements from iter 1 -iter 2 with elements beginning at iter 3 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 32: fig 21_32. cpp // Standard library algorithms iter_swap, swap and swap_ranges. #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 #include <algorithm> 9 10 11 12 13 14 int main() { const int SIZE = 10; int a[ SIZE ] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; std: : ostream_iterator< int > output( cout, " " ); Outline 113 fig 21_32. cpp (1 of 2) // algorithm definitions 15 16 17 cout << "Array a contains: n "; std: : copy( a, a + SIZE, output ); 18 19 20 // swap elements at locations 0 and 1 of array a std: : swap( a[ 0 ], a[ 1 ] ); 21 22 23 24 cout << "n. Array a after swapping a[0] and a[1] " << "using swap: n "; std: : copy( a, a + SIZE, output ); 25 2003 Prentice Hall, Inc. All rights reserved.

26 27 28 29 30 31 // use iterators to swap elements at locations // 0 and 1 of array a std: : iter_swap( &a[ 0 ], &a[ 1 ] ); cout << "n. Array a after swapping a[0] and a[1] " << "using iter_swap: n "; std: : copy( a, a + SIZE, output ); 32 33 34 35 // swap elements in first five elements of array a with // elements in last five elements of array a std: : swap_ranges( a, a + 5 ); 36 37 38 39 cout << "n. Array a after swapping the first five elementsn" << "with the last five elements: n "; std: : copy( a, a + SIZE, output ); 40 41 cout << endl; 42 43 return 0; 44 45 Outline 114 fig 21_32. cpp (2 of 2) } // end main 2003 Prentice Hall, Inc. All rights reserved.

Array a contains: 1 2 3 4 5 6 7 8 9 10 Array a after swapping a[0] and a[1] using swap: 2 1 3 4 5 6 7 8 9 10 Array a after swapping a[0] and a[1] using iter_swap: 1 2 3 4 5 6 7 8 9 10 Array a after swapping the first five elements with the last five elements: 6 7 8 9 10 1 2 3 4 5 Outline 115 fig 21_32. cpp output (1 of 1) 2003 Prentice Hall, Inc. All rights reserved.

21. 5. 8 copy_backward, merge, unique and reverse • copy_backward(iter 1, iter 2, iter 3) – Copy elements from iter 1 -iter 2 to iter 3, in reverse order • merge(iter 1, iter 2, iter 3, iter 4, iter 5) – Ranges iter 1 -iter 2 and iter 3 -iter 4 must be sorted in ascending order – merge copies both lists into iter 5, in ascending order • unique(iter 1, iter 2) – Removes duplicate elements from a sorted list – Returns iterator to new end of sequence • reverse(iter 1, iter 2) – Reverses elements from iter 1 -iter 2 2003 Prentice Hall, Inc. All rights reserved. 116

1 2 3 4 // Fig. 21. 33: fig 21_33. cpp // Standard library functions copy_backward, merge, // unique and reverse. #include <iostream> 5 6 7 using std: : cout; using std: : endl; 8 9 10 #include <algorithm> #include <vector> 11 12 13 14 15 16 17 18 19 Outline 117 fig 21_33. cpp (1 of 3) // algorithm definitions // vector class-template definition int main() { const int SIZE = 5; int a 1[ SIZE ] = { 1, 3, 5, 7, 9 }; int a 2[ SIZE ] = { 2, 4, 5, 7, 9 }; std: : vector< int > v 1( a 1, a 1 + SIZE ); std: : vector< int > v 2( a 2, a 2 + SIZE ); 20 21 std: : ostream_iterator< int > output( cout, " " ); 22 23 24 25 26 cout << "Vector v 1 contains: "; std: : copy( v 1. begin(), v 1. end(), output ); cout << "n. Vector v 2 contains: " ; std: : copy( v 2. begin(), v 2. end(), output ); 2003 Prentice Hall, Inc. All rights reserved.

27 28 std: : vector< int > results( v 1. size() ); 29 30 31 // place elements of v 1 into results in reverse order std: : copy_backward( v 1. begin(), v 1. end(), results. end() ); 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 Outline 118 fig 21_33. cpp (2 of 3) cout << "nn. After copy_backward, results contains: " ; std: : copy( results. begin(), results. end(), output ); std: : vector< int > results 2( v 1. size() + v 2. size() ); // merge elements of v 1 and v 2 into results 2 in sorted order std: : merge( v 1. begin(), v 1. end(), v 2. begin(), v 2. end(), results 2. begin() ); cout << "nn. After merge of v 1 and v 2 results 2 contains: n" ; std: : copy( results 2. begin(), results 2. end(), output ); // eliminate duplicate values from results 2 std: : vector< int >: : iterator end. Location; end. Location = std: : unique( results 2. begin(), results 2. end() ); cout << "nn. After unique results 2 contains: n" ; std: : copy( results 2. begin(), end. Location, output ); 2003 Prentice Hall, Inc. All rights reserved.

53 54 55 56 cout << "nn. Vector v 1 after reverse: " ; // reverse elements of v 1 std: : reverse( v 1. begin(), v 1. end() ); 57 58 std: : copy( v 1. begin(), v 1. end(), output ); 59 60 cout << endl; 61 62 return 0; 63 64 Outline 119 fig 21_33. cpp (3 of 3) fig 21_33. cpp output (1 of 1) } // end main Vector v 1 contains: 1 3 5 7 9 Vector v 2 contains: 2 4 5 7 9 After copy_backward, results contains: 1 3 5 7 9 After merge of v 1 and v 2 results 2 contains: 1 2 3 4 5 5 7 7 9 9 After unique results 2 contains: 1 2 3 4 5 7 9 Vector v 1 after reverse: 9 7 5 3 1 2003 Prentice Hall, Inc. All rights reserved.

21. 5. 9 inplace_merge, unique_copy and reverse_copy • inplace_merge(iter 1, iter 2, iter 3) – Merges two sorted sequences (iter 1 -iter 2, iter 2 -iter 3) inside the same container • unique_copy(iter 1, iter 2, iter 3) – Copies all unique elements in sorted array (from iter 1 -iter 2) into iter 3 • reverse_copy(iter 1, iter 2, iter 3) – Reverses elements in iter 1 -iter 2, copies into iter 3 2003 Prentice Hall, Inc. All rights reserved. 120

1 2 3 4 // Fig. 21. 34: fig 21_34. cpp // Standard library algorithms inplace_merge, // reverse_copy and unique_copy. #include <iostream> 5 6 7 using std: : cout; using std: : endl; 8 9 10 11 #include <algorithm> #include <vector> #include <iterator> 12 13 14 15 16 17 int main() { const int SIZE = 10; int a 1[ SIZE ] = { 1, 3, 5, 7, 9, 1, 3, 5, 7, 9 }; std: : vector< int > v 1( a 1, a 1 + SIZE ); Outline 121 fig 21_34. cpp (1 of 2) // algorithm definitions // vector class-template definition // back_inserter definition 18 19 std: : ostream_iterator< int > output( cout, " " ); 20 21 22 cout << "Vector v 1 contains: "; std: : copy( v 1. begin(), v 1. end(), output ); 23 24 25 26 // merge first half of v 1 with second half of v 1 such that // v 1 contains sorted set of elements after merge std: : inplace_merge( v 1. begin(), v 1. begin() + 5, v 1. end() ); 27 2003 Prentice Hall, Inc. All rights reserved.

28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 cout << "n. After inplace_merge, v 1 contains: " ; std: : copy( v 1. begin(), v 1. end(), output ); std: : vector< int > results 1; // copy only unique elements of v 1 into results 1 std: : unique_copy( v 1. begin(), v 1. end(), std: : back_inserter( results 1 ) ); fig 21_34. cpp (2 of 2) cout << "n. After unique_copy results 1 contains: " ; std: : copy( results 1. begin(), results 1. end(), output ); std: : vector< int > results 2; cout << "n. After reverse_copy, results 2 contains: " ; // copy elements of v 1 into results 2 in reverse order std: : reverse_copy( v 1. begin(), v 1. end(), std: : back_inserter( results 2 ) ); 47 48 std: : copy( results 2. begin(), results 2. end(), output ); 49 50 cout << endl; 51 52 return 0; 53 54 Outline 122 } // end main 2003 Prentice Hall, Inc. All rights reserved.

Vector v 1 contains: 1 3 5 7 9 After inplace_merge, v 1 contains: 1 1 3 3 5 5 7 7 9 9 After unique_copy results 1 contains: 1 3 5 7 9 After reverse_copy, results 2 contains: 9 9 7 7 5 5 3 3 1 1 Outline 123 fig 21_34. cpp output (1 of 1) 2003 Prentice Hall, Inc. All rights reserved.

124 21. 5. 10 Set Operations • includes(iter 1, iter 2, iter 3, iter 4) – Returns true if iter 1 -iter 2 contains iter 3 -iter 4 – Both ranges must be sorted a 1: 1 2 3 4 a 2: 1 3 a 1 includes a 3 • set_difference(iter 1, iter 2, iter 3, iter 4, iter 5) – Copies elements in first set (1 -2) that are not in second set (3 -4) into iter 5 • set_intersection(iter 1, iter 2, iter 3, iter 4, iter 5) – Copies common elements from the two sets (1 -2, 3 -4) into iter 5 2003 Prentice Hall, Inc. All rights reserved.

125 21. 5. 10 Set Operations • set_symmetric_difference(iter 1, iter 2, iter 3, iter 4, iter 5) – Copies elements in set (1 -2) but not set (3 -4), and vice versa, into iter 5 • a 1: 1 2 3 4 5 6 7 8 9 10 • a 2: 4 5 6 7 8 • set_symmetric_difference: 1 2 3 9 10 – Both sets must be sorted • set_union( iter 1, iter 2, iter 3, iter 4, iter 5) – Copies elements in either or both sets to iter 5 – Both sets must be sorted 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 4 // Fig. 21. 35: fig 21_35. cpp // Standard library algorithms includes, set_difference, // set_intersection, set_symmetric_difference and set_union. #include <iostream> 5 6 7 using std: : cout; using std: : endl; 8 9 #include <algorithm> 10 11 12 13 14 15 16 17 int main() { const int SIZE 1 = 10, SIZE 2 = 5, SIZE 3 = 20; int a 1[ SIZE 1 ] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; int a 2[ SIZE 2 ] = { 4, 5, 6, 7, 8 }; int a 3[ SIZE 2 ] = { 4, 5, 6, 11, 15 }; std: : ostream_iterator< int > output( cout, " " ); 18 19 20 21 22 23 24 Outline 126 fig 21_35. cpp (1 of 3) // algorithm definitions cout << "a 1 contains: "; std: : copy( a 1, a 1 + SIZE 1, output ); cout << "na 2 contains: "; std: : copy( a 2, a 2 + SIZE 2, output ); cout << "na 3 contains: "; std: : copy( a 3, a 3 + SIZE 2, output ); 25 2003 Prentice Hall, Inc. All rights reserved.

26 27 28 29 30 31 32 33 34 35 36 // determine whether set a 2 is completely contained in a 1 if ( std: : includes( a 1, a 1 + SIZE 1, a 2 + SIZE 2 ) ) cout << "nna 1 includes a 2"; else cout << "nna 1 does not include a 2" ; Outline 127 fig 21_35. cpp (2 of 3) // determine whether set a 3 is completely contained in a 1 if ( std: : includes( a 1, a 1 + SIZE 1, a 3 + SIZE 2 ) ) cout << "na 1 includes a 3"; else cout << "na 1 does not include a 3" ; 37 38 int difference[ SIZE 1 ]; 39 40 41 42 // determine elements of a 1 not in a 2 int *ptr = std: : set_difference( a 1, a 1 + SIZE 1, a 2 + SIZE 2, difference ); 43 44 45 cout << "nnset_difference of a 1 and a 2 is: " ; std: : copy( difference, ptr, output ); 46 47 intersection[ SIZE 1 ]; 48 49 50 51 // determine elements in both a 1 and a 2 ptr = std: : set_intersection( a 1, a 1 + SIZE 1, a 2 + SIZE 2, intersection ); 52 2003 Prentice Hall, Inc. All rights reserved.

53 54 cout << "nnset_intersection of a 1 and a 2 is: " ; std: : copy( intersection, ptr, output ); 55 56 57 58 59 60 61 // determine elements of a 1 that are not in a 2 and // elements of a 2 that are not in a 1 ptr = std: : set_symmetric_difference( a 1, a 1 + SIZE 1, a 2 + SIZE 2, symmetric_difference ); 62 63 64 cout << "nnset_symmetric_difference of a 1 and a 2 is: " ; std: : copy( symmetric_difference, ptr, output ); 65 66 int union. Set[ SIZE 3 ]; 67 68 69 70 // determine elements that are in either or both sets ptr = std: : set_union( a 1, a 1 + SIZE 1, a 3 + SIZE 2, union. Set ); 71 72 73 74 75 76 77 78 79 int symmetric_difference[ SIZE 1 ]; Outline 128 fig 21_35. cpp (3 of 3) cout << "nnset_union of a 1 and a 3 is: " ; std: : copy( union. Set, ptr, output ); cout << endl; return 0; } // end main 2003 Prentice Hall, Inc. All rights reserved.

a 1 contains: 1 2 3 4 5 6 7 8 9 10 a 2 contains: 4 5 6 7 8 a 3 contains: 4 5 6 11 15 a 1 includes a 2 a 1 does not include a 3 Outline 129 fig 21_35. cpp output (1 of 1) set_difference of a 1 and a 2 is: 1 2 3 9 10 set_intersection of a 1 and a 2 is: 4 5 6 7 8 set_symmetric_difference of a 1 and a 2 is: 1 2 3 9 10 set_union of a 1 and a 3 is: 1 2 3 4 5 6 7 8 9 10 11 15 2003 Prentice Hall, Inc. All rights reserved.

21. 5. 11 lower_bound, upper_bound and equal_range • lower_bound(iter 1, iter 2, value) – For sorted elements, returns iterator to the first location where value could be inserted and elements remain sorted • upper_bound(iter 1, iter 2, value) – Same as lower_bound, but returns iterator to last element where value could be inserted • equal_range(iter 1, iter 2, value) – Returns two iterators, a lower_bound an upper_bound – Assign them to a pair object 2003 Prentice Hall, Inc. All rights reserved. 130

1 2 3 4 // Fig. 21. 36: fig 21_36. cpp // Standard library functions lower_bound, upper_bound and // equal_range for a sorted sequence of values. #include <iostream> 5 6 7 using std: : cout; using std: : endl; 8 9 10 #include <algorithm> #include <vector> 11 12 13 14 15 16 17 int main() { const int SIZE = 10; int a 1[] = { 2, 2, 4, 4, 4, 6, 6, 8 }; std: : vector< int > v( a 1, a 1 + SIZE ); std: : ostream_iterator< int > output( cout, " " ); 18 19 20 21 22 23 24 25 Outline 131 fig 21_36. cpp (1 of 4) // algorithm definitions // vector class-template definition cout << "Vector v contains: n"; std: : copy( v. begin(), v. end(), output ); // determine lower-bound insertion point for 6 in v std: : vector< int >: : iterator lower; lower = std: : lower_bound( v. begin(), v. end(), 6 ); 2003 Prentice Hall, Inc. All rights reserved.

26 27 28 29 30 31 32 33 34 cout << "nn. Lower bound of 6 is element " << ( lower - v. begin() ) << " of vector v"; // determine upper-bound insertion point for 6 in v std: : vector< int >: : iterator upper; upper = std: : upper_bound( v. begin(), v. end(), 6 ); Outline 132 fig 21_36. cpp (2 of 4) cout << "n. Upper bound of 6 is element " << ( upper - v. begin() ) << " of vector v"; 35 36 37 38 39 40 // use equal_range to determine both the lower- and // upper-bound insertion points for 6 std: : pair< std: : vector< int >: : iterator, std: : vector< int >: : iterator > eq; eq = std: : equal_range( v. begin(), v. end(), 6 ); 41 42 43 44 45 46 cout << << << cout << << 47 48 49 cout << "nn. Use lower_bound to locate the first pointn" << "at which 5 can be inserted in order" ; "n. Using equal_range: n" " Lower bound of 6 is element " ( eq. first - v. begin() ) << " of vector v"; "n Upper bound of 6 is element " ( eq. second - v. begin() ) << " of vector v"; 50 2003 Prentice Hall, Inc. All rights reserved.

51 52 // determine lower-bound insertion point for 5 in v lower = std: : lower_bound( v. begin(), v. end(), 5 ); 53 54 55 cout << "n Lower bound of 5 is element " << ( lower - v. begin() ) << " of vector v"; 56 57 58 cout << "nn. Use upper_bound to locate the last pointn" << "at which 7 can be inserted in order" ; 59 60 61 // determine upper-bound insertion point for 7 in v upper = std: : upper_bound( v. begin(), v. end(), 7 ); 62 63 64 cout << "n Upper bound of 7 is element " << ( upper - v. begin() ) << " of vector v"; 65 66 67 cout << "nn. Use equal_range to locate the first andn" << "last point at which 5 can be inserted in order" ; 68 69 70 71 // use equal_range to determine both the lower- and // upper-bound insertion points for 5 eq = std: : equal_range( v. begin(), v. end(), 5 ); 72 73 74 75 76 77 cout << << << Outline 133 fig 21_36. cpp (3 of 4) "n Lower bound of 5 is element " ( eq. first - v. begin() ) << " of vector v"; "n Upper bound of 5 is element " ( eq. second - v. begin() ) << " of vector v" endl; 2003 Prentice Hall, Inc. All rights reserved.

78 79 80 81 Outline return 0; } // end main fig 21_36. cpp (4 of 4) Vector v contains: 2 2 4 4 4 6 6 8 Lower bound of 6 is Upper bound of 6 is Using equal_range: Lower bound of 6 Upper bound of 6 134 element 5 of vector v element 9 of vector v fig 21_36. cpp output (1 of 1) is element 5 of vector v is element 9 of vector v Use lower_bound to locate the first point at which 5 can be inserted in order Lower bound of 5 is element 5 of vector v Use upper_bound to locate the last point at which 7 can be inserted in order Upper bound of 7 is element 9 of vector v Use equal_range to locate the first and last point at which 5 can be inserted in order Lower bound of 5 is element 5 of vector v Upper bound of 5 is element 5 of vector v 2003 Prentice Hall, Inc. All rights reserved.

135 21. 5. 12 Heapsort • Heapsort - sorting algorithm – – Heap binary tree Largest element at top of heap Children always less than parent node make_heap(iter 1, iter 2) • Creates a heap in the range of the iterators • Must be random access iterators (arrays, vectors, deques) – sort_heap(iter 1, iter 2) • Sorts a heap sequence from iter 1 to iter 2 2003 Prentice Hall, Inc. All rights reserved.

136 21. 5. 12 Heapsort • Functions – push_heap(iter 1, iter 2) • The iterators must specify a heap • Adds last element in object to heap – Assumes other elements already in heap order – pop_heap(iter 1, iter 2) • Removes the top element of a heap and puts it at the end of the container. • Function checks that all other elements still in a heap • Range of the iterators must be a heap. • If all the elements popped, sorted list 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 4 // Fig. 21. 37: fig 21_37. cpp // Standard library algorithms push_heap, pop_heap, // make_heap and sort_heap. #include <iostream> 5 6 7 using std: : cout; using std: : endl; 8 9 10 #include <algorithm> #include <vector> 11 12 13 14 15 16 17 int main() { const int SIZE = 10; int a[ SIZE ] = { 3, 100, 52, 77, 22, 31, 1, 98, 13, 40 }; std: : vector< int > v( a, a + SIZE ), v 2; std: : ostream_iterator< int > output( cout, " " ); 18 19 20 21 22 23 24 25 26 cout << "Vector v before make_heap: n" ; std: : copy( v. begin(), v. end(), output ); Outline 137 fig 21_37. cpp (1 of 3) Create a new heap. // create heap from vector v std: : make_heap( v. begin(), v. end() ); cout << "n. Vector v after make_heap: n" ; std: : copy( v. begin(), v. end(), output ); 2003 Prentice Hall, Inc. All rights reserved.

27 28 29 30 31 32 fig 21_37. cpp (2 of 3) cout << "n. Vector v after sort_heap: n" ; std: : copy( v. begin(), v. end(), output ); 33 34 35 36 // perform the heapsort with push_heap and pop_heap cout << "nn. Array a contains: " ; std: : copy( a, a + SIZE, output ); 37 38 cout << endl; 39 40 41 42 43 44 45 46 // place elements of array a into v 2 and Add elements // maintain elements of v 2 in heap for ( int i = 0; i < SIZE; ++i ) { v 2. push_back( a[ i ] ); std: : push_heap( v 2. begin(), v 2. end() ); cout << "nv 2 after push_heap(a[" << i << "]): "; std: : copy( v 2. begin(), v 2. end(), output ); 47 48 49 50 Outline // sort elements of v with sort_heap std: : sort_heap( v. begin(), v. end() ); 138 one at a time. } // end for cout << endl; 51 2003 Prentice Hall, Inc. All rights reserved.

52 53 54 55 56 // remove elements from heap in sorted order for ( int j = 0; j < v 2. size(); ++j ) { cout << "nv 2 after " << v 2[ 0 ] << " popped from heapn"; std: : pop_heap( v 2. begin(), v 2. end() - j ); std: : copy( v 2. begin(), v 2. end(), output ); 57 58 } // end for 59 60 cout << endl; 61 62 return 0; 63 64 Outline 139 fig 21_37. cpp (3 of 3) } // end main 2003 Prentice Hall, Inc. All rights reserved.

Vector v before make_heap: 3 100 52 77 22 31 1 98 13 40 Vector v after make_heap: 100 98 52 77 40 31 1 3 13 22 Vector v after sort_heap: 1 3 13 22 31 40 52 77 98 100 Outline 140 fig 21_37. cpp output (1 of 2) Array a contains: 3 100 52 77 22 31 1 98 13 40 v 2 v 2 v 2 after after after push_heap(a[0]): push_heap(a[1]): push_heap(a[2]): push_heap(a[3]): push_heap(a[4]): push_heap(a[5]): push_heap(a[6]): push_heap(a[7]): push_heap(a[8]): push_heap(a[9]): 3 100 100 100 3 3 52 77 52 98 52 3 3 22 31 1 77 22 31 1 3 13 77 40 31 1 3 13 22 2003 Prentice Hall, Inc. All rights reserved.

v 2 after 100 popped from heap 98 77 52 22 40 31 1 3 13 100 v 2 after 98 popped from heap 77 40 52 22 13 31 1 3 98 100 v 2 after 77 popped from heap 52 40 31 22 13 3 1 77 98 100 v 2 after 52 popped from heap 40 22 31 1 13 3 52 77 98 100 v 2 after 40 popped from heap 31 22 3 1 13 40 52 77 98 100 v 2 after 31 popped from heap 22 13 3 1 31 40 52 77 98 100 v 2 after 22 popped from heap 13 1 3 22 31 40 52 77 98 100 v 2 after 13 popped from heap 3 1 13 22 31 40 52 77 98 100 v 2 after 3 popped from heap 1 3 13 22 31 40 52 77 98 100 v 2 after 1 popped from heap 1 3 13 22 31 40 52 77 98 100 Outline 141 fig 21_37. cpp output (2 of 2) 2003 Prentice Hall, Inc. All rights reserved.

142 21. 5. 13 min and max • min(value 1, value 2) – Returns smaller element • max(value 1, value 2) – Returns larger element 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 38: fig 21_38. cpp // Standard library algorithms min and max. #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 #include <algorithm> 9 10 11 12 13 14 15 16 17 18 19 int main() { cout << << 20 21 22 23 Outline 143 fig 21_38. cpp (1 of 1) "The minimum of 12 and 7 is: " std: : min( 12, 7 ); "n. The maximum of 12 and 7 is: " std: : max( 12, 7 ); "n. The minimum of 'G' and 'Z' is: " std: : min( 'G', 'Z' ); "n. The maximum of 'G' and 'Z' is: " std: : max( 'G', 'Z' ) << endl; return 0; } // end main 2003 Prentice Hall, Inc. All rights reserved.

The The minimum maximum of of 12 and 7 is: 7 12 and 7 is: 12 'G' and 'Z' is: G 'G' and 'Z' is: Z Outline 144 fig 21_38. cpp output (1 of 1) 2003 Prentice Hall, Inc. All rights reserved.

21. 5. 14 Algorithms Not Covered in This Chapter • • • • adjacent_difference inner_product partial_sum nth_element partition stable_partition next_permutation prev_permutation rotate_copy adjacent_find partial_sort_copy stable_sort 2003 Prentice Hall, Inc. All rights reserved. 145

146 21. 6 Class bitset • Class bitset – Represents a set of bit flags – Can manipulate bit sets • Operations – – – – – bitset <size> b; create bitset b. set( bit. Number) set bit. Number to on b. set() all bits on b. reset(bit. Number) set bit. Number to off b. reset() all bits off b. flip(bit. Number) flip bit (on to off, off to on) b. flip() flip all bits b[bit. Number] returns reference to bit b. at(bit. Number) range checking, returns reference 2003 Prentice Hall, Inc. All rights reserved.

147 21. 6 Class bitset • Operations b. test(bit. Number) has range checking; if bit on, returns true b. size() size of bitset b. count() number of bits set to on b. any() true if any bits are on b. none() true if no bits are on can use &=, |=, !=, <<=, >>= – b &= b 1 – Logical AND between b and b 1, result in b • b. to_string() convert to string • b. to_ulong() convert to long • • • 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 40: fig 21_40. cpp // Using a bitset to demonstrate the Sieve of Eratosthenes. #include <iostream> 4 5 6 7 using std: : cin; using std: : cout; using std: : endl; 8 9 #include <iomanip> 10 11 using std: : setw; 12 13 14 #include <bitset> #include <cmath> 15 16 17 18 19 20 int main() { const int size = 1024; int value; std: : bitset< size > sieve; 21 22 Outline 148 fig 21_40. cpp (1 of 3) // bitset class definition // sqrt prototype sieve. flip(); 23 2003 Prentice Hall, Inc. All rights reserved.

24 25 // perform Sieve of Eratosthenes int final. Bit = sqrt( sieve. size() ) + 1; 26 27 for ( int i = 2; i < final. Bit; ++i ) 28 29 30 31 32 if ( sieve. test( i ) ) Outline Sieve of Eratosthenes: turn off bits for all multiples of a number. What bits remain are fig 21_40. cpp prime. (2 of 3) for ( int j = 2 * i; j < size; j += i ) sieve. reset( j ); 33 34 cout << "The prime numbers in the range 2 to 1023 are: n" ; 35 36 37 // display prime numbers in range 2 -1023 for ( int k = 2, counter = 0; k < size; ++k ) 38 39 40 41 42 43 44 45 46 47 149 if ( sieve. test( k ) ) { cout << setw( 5 ) << k; if ( ++counter % 12 == 0 ) cout << 'n'; } // end outer if cout << endl; 48 2003 Prentice Hall, Inc. All rights reserved.

49 50 51 // get value from user to determine whether value is prime cout << "n. Enter a value from 1 to 1023 (-1 to end): " ; cin >> value; 52 53 while ( value != -1 ) { 54 55 56 57 58 59 60 61 fig 21_40. cpp (3 of 3) if ( sieve[ value ] ) cout << value << " is a prime numbern"; else cout << value << " is not a prime numbern" ; cout << "n. Enter a value from 2 to 1023 (-1 to end): " ; cin >> value; 62 63 } // end while 64 65 return 0; 66 67 Outline 150 } // end main 2003 Prentice Hall, Inc. All rights reserved.

The prime numbers in the range 2 to 1023 are: 2 3 5 7 11 13 17 19 23 41 43 47 53 59 61 67 71 73 97 101 103 107 109 113 127 131 137 157 163 167 173 179 181 193 197 229 233 239 241 257 263 269 283 293 307 311 313 317 331 337 347 367 373 379 383 389 397 401 409 419 439 443 449 457 461 463 467 479 487 509 521 523 541 547 557 563 569 571 599 601 607 613 617 619 631 643 661 673 677 683 691 709 719 727 751 757 761 769 773 787 797 809 811 829 839 853 857 859 863 877 881 883 919 929 937 941 947 953 967 971 977 1009 1013 1019 1021 29 79 139 199 271 349 421 491 577 647 733 821 887 983 31 83 149 211 277 353 431 499 587 653 739 823 907 991 37 89 151 223 281 359 433 503 593 659 743 827 911 997 Outline 151 fig 21_40. cpp output (1 of 1) Enter a value from 1 to 1023 (-1 to end): 389 is a prime number Enter a value from 2 to 1023 (-1 to end): 88 88 is not a prime number Enter a value from 2 to 1023 (-1 to end): -1 2003 Prentice Hall, Inc. All rights reserved.

152 21. 7 Function Objects • Function objects (<functional>) – Contain functions invoked using operator() 2003 Prentice Hall, Inc. All rights reserved.

1 2 3 // Fig. 21. 42: fig 21_42. cpp // Demonstrating function objects. #include <iostream> 4 5 6 using std: : cout; using std: : endl; 7 8 9 10 11 #include 12 13 14 15 16 17 18 19 <vector> <algorithm> <numeric> <functional> Outline 153 fig 21_42. cpp (1 of 4) // // vector class-template definition copy algorithm accumulate algorithm binary_function definition Create a function to be used andwith accumulate. // binary function adds square of its second argument // running total in its first argument, then returns sum int sum. Squares( int total, int value ) { return total + value * value; } // end function sum. Squares 20 2003 Prentice Hall, Inc. All rights reserved.

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 // binary function class template defines overloaded operator() // that adds square of its second argument and running total in // its first argument, then returns sum template< class T > class Sum. Squares. Class : public std: : binary_function< T, T, T > { public: // add square of value to total and return result const T operator()( const T &total, const T &value ) { return total + value * value; Outline 154 fig 21_42. cpp Create a function (2 of 4) object (it can also encapsulate data). Overload operator(). } // end function operator() }; // end class Sum. Squares. Class 37 2003 Prentice Hall, Inc. All rights reserved.

38 39 40 41 int main() { const int SIZE = 10; int array[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; 42 43 std: : vector< int > integers( array, array + SIZE ); 44 45 std: : ostream_iterator< int > output( cout, " " ); 46 47 int result = 0; 48 49 50 cout << "vector v contains: n"; std: : copy( integers. begin(), integers. end(), output ); 51 52 53 54 55 // calculate sum of squares of elements of vector integers // using binary function sum. Squares result = std: : accumulate( integers. begin(), integers. end(), 0, sum. Squares ); 56 57 58 cout << "nn. Sum of squares of elements in integers using " << "binarynfunction sum. Squares: " << result; Outline 155 fig 21_42. cpp (3 of 4) accumulate initially passes 0 as the first argument, with the first element as the second. It then uses the return value as the first argument, and iterates through the other elements. 59 2003 Prentice Hall, Inc. All rights reserved.

60 61 62 63 // calculate sum of squares of elements of vector integers // using binary-function object result = std: : accumulate( integers. begin(), integers. end(), 0, Sum. Squares. Class< int >() ); 64 65 66 67 cout << "nn. Sum of squares of elements in integers using " << "binarynfunction object of type " << "Sum. Squares. Class< int >: " << result << endl; 68 69 return 0; 70 71 Outline 156 fig 21_42. cpp (4 of 4) fig 21_42. cpp output (1 of 1) Use accumulate with a function object. } // end main vector v contains: 1 2 3 4 5 6 7 8 9 10 Sum of squares of elements in integers using binary function sum. Squares: 385 Sum of squares of elements in integers using binary function object of type Sum. Squares. Class< int >: 385 2003 Prentice Hall, Inc. All rights reserved.