C++ Program to Swap Two Numbers

Example 1: Program to Swap Two Numbers (Using Temporary Variable)

#include <iostream>
using namespace std;

int main()
{
    int a = 2, b = 4, temp;

    cout << "Before swapping." << endl;
    cout << "a = " << a << ", b = " << b << endl;

    temp = a;
    a = b;
    b = temp;

    cout << "\nAfter swapping." << endl;
    cout << "a = " << a << ", b = " << b << endl;

    return 0;
}

Output

Before swapping.
a = 2, b = 4

After swapping.
a = 4, b = 2

Working of above Program

In this program, three variables are used.

The contents of the first variable is copied into the temp variable. Then, the contents of second variable is copied to the first variable.
Finally, the contents of the temp variable is copied back to the second variable which completes the swapping process.

You can also perform swapping using only two variables as below.

Example 2: Program to Swap Two Numbers (Without Using Temporary Variable)

#include <iostream>
using namespace std;

int main()
{
    
    int a = 2, b = 4;

    cout << "Before swapping." << endl;
    cout << "a = " << a << ", b = " << b << endl;

    a = a + b;
    b = a - b;
    a = a - b;

    cout << "\nAfter swapping." << endl;
    cout << "a = " << a << ", b = " << b << endl;

    return 0;
}

Output

The output of this program is the same as the first program above.

Before swapping.
a = 2, b = 4

After swapping.
a = 4, b = 2

Working of above Program

Let us see how this program works:

1. Initially, a = 2 and b = 4.
2. Then, we add a and b and store it in a with the code a = a + b. This means a = 2 + 4. So, a = 6 now.
3. Then we use the code b = a - b. This means b = 6 - 2. So, b = 4 now.
4. Again, we use the code a = a - b. This means a = 6 - 4. So finally, a = 2.

Hence, the numbers have been swapped.

Note: We can use multiplication and division instead of addition and subtraction. However, this won't work if one of the numbers is 0.

int a = 2, b = 4;

// using multiplication and division for swapping
a = a * b;    // a = 8
b = a / b;    // b = 2
a = a / b;    // a = 4

Next Example

We hope that this Example helped you develop better understanding of the concept of Swapping Two Numbers in C++.

Keep Learning : )

In the next Example, we will learn about C++ Find ASCII Value of a Character.