C++ Programming Code Examples

/* Program To Implement Doubly Linked List */ #include<iostream> #include<cstdio> #include<cstdlib> /* Node Declaration */ using namespace std; struct node { int info; struct node *next; struct node *prev; }*start; /* Class Declaration */ class double_llist { public: void create_list(int value); void add_begin(int value); void add_after(int value, int position); void delete_element(int value); void search_element(int value); void display_dlist(); void count(); void reverse(); double_llist() { start = NULL; } }; /* Main: Conatins Menu */ int main() { int choice, element, position; double_llist dl; while (1) { cout<<endl<<"----------------------------"<<endl; cout<<endl<<"Operations on Doubly linked list"<<endl; cout<<endl<<"----------------------------"<<endl; cout<<"1.Create Node"<<endl; cout<<"2.Add at begining"<<endl; cout<<"3.Add after position"<<endl; cout<<"4.Delete"<<endl; cout<<"5.Display"<<endl; cout<<"6.Count"<<endl; cout<<"7.Reverse"<<endl; cout<<"8.Quit"<<endl; cout<<"Enter your choice : "; cin>>choice; switch ( choice ) { case 1: cout<<"Enter the element: "; cin>>element; dl.create_list(element); cout<<endl; break; case 2: cout<<"Enter the element: "; cin>>element; dl.add_begin(element); cout<<endl; break; case 3: cout<<"Enter the element: "; cin>>element; cout<<"Insert Element after postion: "; cin>>position; dl.add_after(element, position); cout<<endl; break; case 4: if (start == NULL) { cout<<"List empty,nothing to delete"<<endl; break; } cout<<"Enter the element for deletion: "; cin>>element; dl.delete_element(element); cout<<endl; break; case 5: dl.display_dlist(); cout<<endl; break; case 6: dl.count(); break; case 7: if (start == NULL) { cout<<"List empty,nothing to reverse"<<endl; break; } dl.reverse(); cout<<endl; break; case 8: exit(1); default: cout<<"Wrong choice"<<endl; } } return 0; } /* Create Double Link List */ void double_llist::create_list(int value) { struct node *s, *temp; temp = new(struct node); temp->info = value; temp->next = NULL; if (start == NULL) { temp->prev = NULL; start = temp; } else { s = start; while (s->next != NULL) s = s->next; s->next = temp; temp->prev = s; } } /* Insertion at the beginning */ void double_llist::add_begin(int value) { if (start == NULL) { cout<<"First Create the list."<<endl; return; } struct node *temp; temp = new(struct node); temp->prev = NULL; temp->info = value; temp->next = start; start->prev = temp; start = temp; cout<<"Element Inserted"<<endl; } /* Insertion of element at a particular position */ void double_llist::add_after(int value, int pos) { if (start == NULL) { cout<<"First Create the list."<<endl; return; } struct node *tmp, *q; int i; q = start; for (i = 0;i < pos - 1;i++) { q = q->next; if (q == NULL) { cout<<"There are less than "; cout<<pos<<" elements."<<endl; return; } } tmp = new(struct node); tmp->info = value; if (q->next == NULL) { q->next = tmp; tmp->next = NULL; tmp->prev = q; } else { tmp->next = q->next; tmp->next->prev = tmp; q->next = tmp; tmp->prev = q; } cout<<"Element Inserted"<<endl; } /* Deletion of element from the list */ void double_llist::delete_element(int value) { struct node *tmp, *q; /*first element deletion*/ if (start->info == value) { tmp = start; start = start->next; start->prev = NULL; cout<<"Element Deleted"<<endl; free(tmp); return; } q = start; while (q->next->next != NULL) { /*Element deleted in between*/ if (q->next->info == value) { tmp = q->next; q->next = tmp->next; tmp->next->prev = q; cout<<"Element Deleted"<<endl; free(tmp); return; } q = q->next; } /*last element deleted*/ if (q->next->info == value) { tmp = q->next; free(tmp); q->next = NULL; cout<<"Element Deleted"<<endl; return; } cout<<"Element "<<value<<" not found"<<endl; } /* Display elements of Doubly Link List */ void double_llist::display_dlist() { struct node *q; if (start == NULL) { cout<<"List empty,nothing to display"<<endl; return; } q = start; cout<<"The Doubly Link List is :"<<endl; while (q != NULL) { cout<<q->info<<" <-> "; q = q->next; } cout<<"NULL"<<endl; } /* Number of elements in Doubly Link List */ void double_llist::count() { struct node *q = start; int cnt = 0; while (q != NULL) { q = q->next; cnt++; } cout<<"Number of elements are: "<<cnt<<endl; } /* Reverse Doubly Link List */ void double_llist::reverse() { struct node *p1, *p2; p1 = start; p2 = p1->next; p1->next = NULL; p1->prev = p2; while (p2 != NULL) { p2->prev = p2->next; p2->next = p1; p1 = p2; p2 = p2->prev; } start = p1; cout<<"List Reversed"<<endl; }

/* C++ allows us to allocate the memory of a variable or an array in run time. This is known as dynamic memory allocation. The new operator denotes a request for memory allocation on the Free Store. If sufficient memory is available, new operator initializes the memory and returns the address of the newly allocated and initialized memory to the pointer variable. */ /* Allocate storage space by operator new */ // C++ program code example to illustrate dynamic allocation and deallocation of memory using new and delete #include <iostream> using namespace std; int main () { // Pointer initialization to null int* p = NULL; // Request memory for the variable // using new operator p = new(nothrow) int; if (!p) cout << "allocation of memory failed\n"; else { // Store value at allocated address *p = 29; cout << "Value of p: " << *p << endl; } // Request block of memory // using new operator float *r = new float(75.25); cout << "Value of r: " << *r << endl; // Request block of memory of size n int n = 5; int *q = new(nothrow) int[n]; if (!q) cout << "allocation of memory failed\n"; else { for (int i = 0; i < n; i++) q[i] = i+1; cout << "Value store in block of memory: "; for (int i = 0; i < n; i++) cout << q[i] << " "; } // freed the allocated memory delete p; delete r; // freed the block of allocated memory delete[] q; return 0; }

/* the switch statement helps in testing the equality of a variable against a set of values */ #include <iostream> using namespace std; int main () { // local variable declaration: char grade = 'D'; switch(grade) { case 'A' : cout << "Excellent!" << endl; break; case 'B' : case 'C' : cout << "Well done" << endl; break; case 'D' : cout << "You passed" << endl; break; case 'F' : cout << "Better try again" << endl; break; default : cout << "Invalid grade" << endl; } cout << "Your grade is " << grade << endl; return 0; }

/* using #include directive in C language */ #include <stdio.h> int main() { /* * C standard library printf function * defined in the stdio.h header file */ printf("I love you Clementine"); printf("I love you so much"); printf("HappyCodings"); return 0; }

/* simple code example by main() function in C++ */ #include <iostream> using namespace std; int main() { int day = 4; switch (day) { case 1: cout << "Monday"; break; case 2: cout << "Tuesday"; break; case 3: cout << "Wednesday"; break; case 4: cout << "Thursday"; break; case 5: cout << "Friday"; break; case 6: cout << "Saturday"; break; case 7: cout << "Sunday"; break; } return 0; }

/* Structure is a collection of variables of different data types under a single name. It is similar to a class in that, both holds a collecion of data of different data types. */ #include <iostream> using namespace std; struct Person { char name[50]; int age; float salary; }; int main() { Person p1; cout << "Enter Full name: "; cin.get(p1.name, 50); cout << "Enter age: "; cin >> p1.age; cout << "Enter salary: "; cin >> p1.salary; cout << "\nDisplaying Information." << endl; cout << "Name: " << p1.name << endl; cout <<"Age: " << p1.age << endl; cout << "Salary: " << p1.salary; return 0; }

/* If Else Statement in C++ Language */ #include <iostream> using namespace std; int main () { // local variable declaration: int a = 100; // check the boolean condition if( a < 20 ) { // if condition is true then print the following cout << "a is less than 20;" << endl; } else { // if condition is false then print the following cout << "a is not less than 20;" << endl; } cout << "value of a is : " << a << endl; return 0; }

/* break statement with while loop code example */ // program to find the sum of positive numbers // if the user enters a negative numbers, break ends the loop // the negative number entered is not added to sum #include <iostream> using namespace std; int main() { int number; int sum = 0; while (true) { // take input from the user cout << "Enter a number: "; cin >> number; // break condition if (number < 0) { break; } // add all positive numbers sum += number; } // display the sum cout << "The sum is " << sum << endl; return 0; }

/* For Loop Statement in C++ Language */ // C++ program to find the sum of first n natural numbers // positive integers such as 1,2,3,...n are known as natural numbers #include <iostream> using namespace std; int main() { int num, sum; sum = 0; cout << "Enter a positive integer: "; cin >> num; for (int i = 1; i <= num; ++i) { sum += i; } cout << "Sum = " << sum << endl; return 0; }

/* namespaces in C++ language */ // A C++ code to demonstrate that we can define // methods outside namespace. #include <iostream> using namespace std; // Creating a namespace namespace ns { void display(); class happy { public: void display(); }; } // Defining methods of namespace void ns::happy::display() { cout << "ns::happy::display()\n"; } void ns::display() { cout << "ns::display()\n"; } // Driver code int main() { ns::happy obj; ns::display(); obj.display(); return 0; }

/* terminate the process normally, performing the regular cleanup for terminating programs by exit() function code example */ #include<iostream> using namespace std; int main() { int i; cout<<"Enter a non-zero value: "; //user input cin>>i; if(i) // checks whether the user input is non-zero or not { cout<<"Valid input.\n"; } else { cout<<"ERROR!"; //the program exists if the value is 0 exit(0); } cout<<"The input was : "<<i; }

/* Standard end line (endl) in C++ language */ //The header file iostream is imported to enable us to use cout in the program #include <iostream> //a namespace called std is defined using namespace std; //main method is called int main( ) { //cout is used to output the statement cout<< "Welcome to "; //cout is used to output the statement along with endl to start the next statement in the new line and flush the output stream cout<< "C#"<<endl; //cout is used to output the statement along with endl to start the next statement in the new line and flush the output stream cout<< "Learning is fun"<<endl; }

/* using public and private in C++ Class */ // Program to illustrate the working of // public and private in C++ Class #include <iostream> using namespace std; class Room { private: double length; double breadth; double height; public: // function to initialize private variables void initData(double len, double brth, double hgt) { length = len; breadth = brth; height = hgt; } double calculateArea() { return length * breadth; } double calculateVolume() { return length * breadth * height; } }; int main() { // create object of Room class Room room1; // pass the values of private variables as arguments room1.initData(42.5, 30.8, 19.2); cout << "Area of Room = " << room1.calculateArea() << endl; cout << "Volume of Room = " << room1.calculateVolume() << endl; return 0; }

/* Standard Input Stream (cin) in C++ language */ // cin with Member Functions #include <iostream> using namespace std; int main() { char name[20], address[20]; cout << "Name: "; // use cin with getline() cin.getline(name, 20); cout << "Address: "; cin.getline(address, 20); cout << endl << "You entered " << endl; cout << "Name = " << name << endl; cout << "Address = " << address; return 0; }

/* A constructor is a special type of member function that is called automatically when an object is created. In C++, a constructor has the same name as that of the class and it does not have a return type. */ #include <iostream> using namespace std; // declare a class class Wall { private: double length; double height; public: // initialize variables with parameterized constructor Wall(double len, double hgt) { length = len; height = hgt; } // copy constructor with a Wall object as parameter // copies data of the obj parameter Wall(Wall &obj) { length = obj.length; height = obj.height; } double calculateArea() { return length * height; } }; int main() { // create an object of Wall class Wall wall1(10.5, 8.6); // copy contents of wall1 to wall2 Wall wall2 = wall1; // print areas of wall1 and wall2 cout << "Area of Wall 1: " << wall1.calculateArea() << endl; cout << "Area of Wall 2: " << wall2.calculateArea(); return 0; }

/* While Loop Statement in C++ language */ // program to find the sum of positive numbers // if the user enters a negative number, the loop ends // the negative number entered is not added to the sum #include <iostream> using namespace std; int main() { int number; int sum = 0; // take input from the user cout << "Enter a number: "; cin >> number; while (number >= 0) { // add all positive numbers sum += number; // take input again if the number is positive cout << "Enter a number: "; cin >> number; } // display the sum cout << "\nThe sum is " << sum << endl; return 0; }

/* The free() function in C++ deallocates a block of memory previously allocated using calloc, malloc or realloc functions, making it available for further allocations code example. */ #include <iostream> #include <cstdlib> #include <cstring> using namespace std; int main() { char *ptr; ptr = (char*) malloc(10*sizeof(char)); strcpy(ptr,"Hello C++"); cout << "Before reallocating: " << ptr << endl; /* reallocating memory */ ptr = (char*) realloc(ptr,20); strcpy(ptr,"Hello, Welcome to C++"); cout << "After reallocating: " <<ptr << endl; free(ptr); /* prints a garbage value after ptr is free */ cout << endl << "Garbage Value: " << ptr; return 0; }

/* standard output stream (cout) in C++ language */ #include <iostream> using namespace std; int main() { string str = "Do not interrupt me"; char ch = 'm'; // use cout with write() cout.write(str,6); cout << endl; // use cout with put() cout.put(ch); return 0; }