Engineering Problem Solving with C Etter Chapter 6

Engineering Problem Solving with C++, Etter Chapter 6 One-Dimensional Arrays 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 1

One Dimensional Arrays 4 Sorting Algorithms 4 Searching Algorithms 4 Character Strings 4 The string Class. 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 2

Definition and Initialization Computation and Output Function Arguments ARRAYS 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 3

Definition 4 An array is a data structure for storing a contiguous block of data. 4 All data elements in an array must be of the same type. 4 Individual elements of the array are specified using the array name and an offset. 4 In C++ the offset of the first element is always 0. 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 4

Definition and Initialization 4 Syntax: data_type identifier[size] [= initialization list]; Note: size is an integer constant. 4 Example: double m[8]; m[0] m[1] m[2] m[3] m[4] m[5] m[6] m[7] ? ? ? ? 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 5

Initializing Arrays 4 Initializing array elements (initialization=>declaration) char vowels[5] = {'a', 'e', 'i', 'o', 'u'}; bool ans. Key[] ={true, false, true, false}; char word[] = "Hello"; vowels 'a' 'e' ans. Key true word 'H' 'e' 9/17/2020 'i' 'o' false true 'l' 'u' false 'o' Engineering Problem Solving with C++, Second Edition, J. Ingber '' 6

Accessing Array Elements 4 Offsets are used to access individual elements of an array. 4 General format: array_identifier[offset] 4 Example for (int i=0; i<=7; ++i) m[i] = double(i) + 0. 5; 4 Integer expressions may be used as offsets. 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 7

Functions and arrays 4 An array identifier, without subscripts, references the starting address(first element) of the array. 4 In C++, arrays are passed by reference. ie the starting address is passed, no size information. 4 Arrays in C++ to not know their size. 4 Generally we specify an additional parameter representing the number of elements in the array. 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 8

Example #include <iostream> using namespace std; const int MAXSIZE=20; void Read. Arr(double a[], int& count, istream& in); int Find. Min(const double a[], int count); int main( ) { double darr[MAXSIZE]; int cnt=0, position=0; Read. Arr(darr, cnt, cin); position = Find. Min(darr, cnt); cout << "The smallest value in the array is " << darr[position] << endl; } 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 9

// This function inputs values into an array until EOF or array // limit reached void Read. Array(double a[], int& count, istream& in) { double temp; count = 0; in >> temp; while ( (count < MAXSIZE) && !in. eof() ) { a[count] = temp; ++count; in >> temp; } } 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 10

//This function returns the offset of the smallest //value in an array int Find. Min(const double a[], int size) { int offset. Of. Min = 0; for (int i=1; i<size; ++i) { if (a[i] < a[offset. Of. Min] ) { offset. Of. Min = i; }//end if }//end for return offset. Of. Min; }//end Find. Min 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 11

selection sort SORTING ALGORITHMS 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 12

Sorting Algorithms 4 Sorting algorithms arrange the data into either ascending or descending order, based on the values in the array. 4 Sorting algorithms to be discussed – Selection sort 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 13

Selection Sort Algorithm 4 Find minimum value, place it in the first position. 4 Find next minimum value, place it in the second position. 4 Continue doing this until you have placed the second to the largest value in the second to the last position. 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 14

Practice! 4 Fill in the following table to show the array is sorted into ascending order using the selection sort. arr[0] swap min and arr[0] 9/17/2020 29 18 18 arr[1] arr[2] 45 18 45 29 29 45 29 36 Engineering Problem Solving with C++, Second Edition, J. Ingber arr[3] arr[4] 51 51 45 36 36 36 45 51 15

unordered lists SEARCH ALGORITHMS 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 16

Searching Unordered Lists 4 Simple Sequential Search – Examine each element starting with the first one until: • a match is found. • end of the list is reached. 4 Sequential search can be implemented as: – a function which returns true if item in the list, false if item is not in the list. – a function which returns the location of the item if found, or – 1 if not found. 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 17

Searching Ordered Lists 4 Modified Sequential Search: – examine every element in the list until: • item is found. • list element is larger/smaller than the item you are searching for (search fails). 4 Binary Search – Examine middle element: • if element equals item, item found, return location. • if element is larger than item ignore bottom of list. • if element is smaller than item ignore top of list. – Repeat until: • item is found. • top and bottom cross over (search failed). 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 18

Example of Binary Search for 48 5 arr[top] 11 14 22 28 37 43 56 59 70 arr[bot] arr[mid] mid is 7 mid is 5 37 43 56 59 70 arr[top] 37 arr[mid] arr[bot] 43 arr[top] arr[bot] mid is 6 43 arr[6] 43 arr[bot] arr[top] 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 19

C style strings functions defined in cstring CHARACTER STRINGS 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 20

C Style Character Strings 4 A C style strings is defined as a sequence of characters, terminated by the null character. 4 When declaring a character array to store a C style string, memory must be allocated for the null character (''). 4 Literal string constants are enclosed within double quote marks: "a string". 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 21

C Style String Input 4 Recall that the input operator (>>) skips whitespace. 4 To input strings with embedded whitespace , the getline() function can be used as illustrated: char phrase[SIZE]; cin. getline(phrase, SIZE); 4 The getline() function reads up to SIZE-1 characters from the input stream and will insert the null character. 4 getline() is a member function of what class? 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 22

C STYLE STRING FUNCTIONS 4 The Standard C++ library contains a set of predefined functions that operate on C style strings. 4 These functions are defined in the header file: cstring 4 Commonly used string functions: – strlen() – strcpy() – strcat() – strcmp() 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 23

Example: C Style Strings #include <iostream> #include <cstring> //strcmp(), strcpy(), strcat() uses namespace std; int main(){ char str 1[30] = "John", str 2[30] = "Johnson"; char phrase[20] = "'s shirt was green", sentence[30]; if (strcmp(str 1, str 2) < 0) strcpy (sentence, str 1); // puts "John" into sentence else strcpy (sentence, str 2); // puts "Johnson into sentence strcat(sentence, phrase); cout << "Sentence is: " << sentence << endl; return 0; } 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 24

functions defined in string THE STRING CLASS 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 25

The string class 4 The string class implements the concept of a character string. 4 A string object can increase and decrease its size dynamically. 4 Numerous operators and functions are defined in the string class. 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 26

Common Functions Defined in string – size( ) – empty( ) – substr (int start, int len) – c_str() 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 27

Overloaded Operators Defined in string 4 relational operators – < > == <= >= 4 concatenation – + += 4 assignment – = 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 28

Example: string class #include <iostream> #include <string> uses namespace std; int main(){ string str 1 = "John", str 2 = "Johnson"; string phrase = "'s shirt was green", sentence; if (str 1 < str 2) sentence = str 1; // assign "John" to sentence else sentence = str 2; // assign "Johnson to sentence += phrase; // append phrase to sentence cout << "Sentence is: " << sentence << endl; return 0; } 9/17/2020 Engineering Problem Solving with C++, Second Edition, J. Ingber 29