Swap Numbers Using Pointers in C++

Introduction

In this lab, we will learn how to swap two numbers using pointers in C++. The program swaps two numbers by passing their addresses to the function and uses pointers to point to their locations in memory.

Include header files and declare function

First, we include the necessary header files and declare the swap function that takes two integer pointers as arguments.

#include <iostream>
using namespace std;

//Swap function to swap 2 numbers
void swap(int *num1, int *num2);

Define the swap function

Here, we implement the swap function as follows:

void swap(int *num1, int *num2) {
       int temp;
       //Copy the value of num1 to some temp variable
       temp = *num1;

       //Copy the value of num2 to num1
       *num1 = *num2;

       //Copy the value of num1 stored in temp to num2
       *num2 = temp;
}

The function takes in two integer pointers as arguments and swaps the values they point to using a temporary variable.

Input two numbers and call swap function

Declare num1 and num2 variables and use cin to input their values. Call the swap function and pass in their addresses as arguments.

int main() {
       int num1, num2;

       //Inputting 2 numbers from user
       cout<<"Enter the first number : ";
       cin>>num1;
       cout<<"Enter the Second number : ";
       cin>>num2;

       //Passing the addresses of num1 and num2
       swap(&num1, &num2);

Output swapped numbers

Output the swapped numbers using cout.

//Printing the swapped values of num1 and num2
cout<<"First number : "<< num1 << endl;
cout<<"Second number: "<<num2 << endl;

Compile and run the program

Save the program in the ~/project directory as main.cpp. Use the following command to compile the code

g++ main.cpp -o main && ./main

Summary

In this lab, we have learned how to swap two numbers using pointers in C++. We declared and defined a swap function that swapped the values two integer pointers point to and used cin and cout to get user input and display output, respectively.