ECE 250 Data Structures and Algorithms C Tutorial

ECE 250 Data Structures and Algorithms C++ Tutorial Hany Samuel and Douglas Wilhelm Harder Department of Electrical and Computer Engineering University of Waterloo Copyright © 2006 by Douglas Wilhelm Harder. All rights reserved.

C++ Tutorial • In this tutorial we will look at: – C++ statements – data types – variables – pointers – arrays – functions – classes • Examine different examples.

Built-in Data Types Integral Numbers char 8 bits 0, . . . , 28 – 1 = 255 short int 16 bits 15 -2 , . . . , 215 – 1 int 32 bits 31 -2 , . . . , 231 – 1 “Real” numbers bool false == 0 true == 1 float 32 bits ± 1. 18 10– 38 ± 3. 40 10 38 double 64 bits ± 2. 23 10– 308 ± 1. 80 10 308

Example 1 • • The basic parts of the c++ main function. How to declare and initialize variables. How to define constants. How to perform simple input/output operation.

Example 1 • A program to calculate the area of a circle given its radius. #include <iostream> using namespace std; int main() { double radius; const double PI = 3. 14; cout << "Please enter the radius: "; cin >> radius; double area = PI*(radius*radius); cout << "the area is = " << area << endl; return 0; } Preprocessor directives Defining constants Variable declarations and initialization (compare with C#)

Example 2 • Operators: – arithmetic: + * / += -= *= /= – increment, decrement: ++ -- % %= – bitwise operators: & | ~ << >> and, or, and complement left and right bit shifting – comparison: < > <= >= != == – logical conditions: && || ! and , or and not

Example 2 • Loops: for ( initialize; condition; increment ) { } while ( condition ){ } do { } while( condition ); • Conditions if ( condition ) { } else { }

Example 2 • A program to find all the numbers divisible by either 3 or 4 #include <iostream> using namespace std; int main() { int n; cout << "please enter n: "; cin >> n; for( int i = 1; i <= n; ++i ) { if ( i % 3 == 0 || i % 4 == 0 ) { cout << i << endl; } } return 0; }

Example 3 • Java and C# require that functions be defined together with their declaration • In C++, functions – need only be declared in the class – the actual definition may be elsewhere • Example declaration: int factorial( int ); // parameter name optional

Example 3 • Iterative calculation: n! = n(n – 1)(n – 2)⋅⋅⋅2⋅1 #include <iostream> using namespace std; // definition of factorial int factorial( int n ) { int result = 1; // declaration of factorial int factorial(int); // declaration and definition // of main int main() { int n; cout << "Please enter n: "; cin >> n; int result = factorial( n ); cout << result << endl; return 0; } for ( int i = 2; i <= n; ++ i ) { result *= i; } return result; }

Example 3 • Recursive calculation: n! = n(n – 1)! #include <iostream> using namespace std; // declaration of factorial int factorial(int); // declaration and definition // of main int main() { int n; cout << "Please enter n: "; cin >> n; int result = factorial( n ); cout << result << endl; // definition of factorial int factorial( int n ) { if( n == 0 || n == 1 ) { return 1; } return n * factorial( n – 1 ); } Question: Is this program is better: this recursive version or the previous iterative version? Why ? return 0; }

Arrays versus Pointers • An array of five integers: int numbers[5]; • The variable numbers stores the address of the first entry numbers • Access contents numbers[0] using numbers[n] &(numbers[2]) numbers[2]

Example 4 (Arrays) • A program which reads 10 numbers and prints their sum, average, max and min: for( int i = 1; i < 10; ++i ) { if( numbers[i] < min ) { min = numbers[i]; } if( numbers[i] > max ) { max = numbers[i]; } sum += numbers[i]; } #include <iostream> using namespace std; int main() { int numbers[10]; for( int i = 0; i < 10; ++i ) { cin >> numbers[i]; } ave = static_cast<double>(sum)/10. 0; int min; int max; int sum; double ave; cout << << min = max = sum = numbers[0]; "sum = " << "average = " << "maximum = " << "minimum = " << return 0; } sum ave max min << << endl;

Pointers • A pointer is simply a variable which stores a memory address • The type of the variable stored at that address should be known int * ptr 1; double * ptr 2; • Example: int x = 5; int * address; address = &x; cout << “The number at location " << address << " is = " << *address;

Pointers and Dynamic arrays • Array size must be specified at compile time. What about run time ? • Pointers solve that: int * numbers = new int[n]; • Never forget to deallocate the memory: delete [] numbers;

Arrays • Dynamic allocation of an array – new typename[n] requests memory from the OS – delete[] returns the memory to the OS – the new typename[n] operator returns a pointer • Example: int main() { int n, *dynarray; cin >> n; // console in (keyboard) dynarray = new int[n]; // use the array dynarray. . . delete [] dynarray; return 0; }

Classes • An object may be described by: – attributes (descriptions, properties, nouns) – operations (behaviours, verbs) • The following table is a summary of the language-specific terminology: C# C++ attributes member variables Operations methods member functions Attributes

Classes #include <iostream> using namespace std; class Complex { private: double re; double im; void set. Real( double r ) { re = r; } void set. Imag( double i ) { im = i; } Complex add( Complex z ) { double r = re + z. re; double i = im + z. im; return Complex( r, i ); } public: Complex( double r = 0, double i = 0 ): re(r), im(i) { // empty friend void print( Complex ); } }; double real() const { return re; void print ( Complex z ) { } cout << z. real() << " + j " double imag() const { << z. imag(); return im; } }

Classes (cont) int main() { Complex z 1( 3 ); Complex z 2( 4, 5 ); // 3 + 0 j // 4 + 5 j Complex w = z 1. add( z 2 ); print( w ); }