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C Program to Swap Two Numbers without using Third Variable

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In this tutorial, we will write a C program to swap two numbers without using a temporary variable. There are two ways to swap variables.

  1. Using + and –
  2. Using * and /

Let us go through each of them with a C program. You may check out the following program.

C Program to Swap Two Numbers without using Third Variable

1. Using + and –

#include<stdio.h>

int main()
{
    int a, b;
    printf("Enter a: ");
    scanf("%d", &a);
    
    printf("Enter b: ");
    scanf("%d", &b);
    
    
    a = a + b;  //a = 10 + 20 = 30
    b = a - b;  //b = 30 - 20 = 10
    a = a - b;  //a = 30 - 10 = 20
    
    printf("The swapped values a: %d and b: %d", a, b);
    
    return 0;
}

Output:

Enter a: 10
Enter b: 20
The swapped values a: 20 and b: 10

2. Using * and / 

#include<stdio.h>

int main()
{
    int a, b;
    printf("Enter a: ");
    scanf("%d", &a);
    
    printf("Enter b: ");
    scanf("%d", &b);
    
    a = a * b; //a = 10 * 20 = 200
    b = a / b; //b = 200 / 20 = 10
    a = a / b; //a = 200 / 10 = 20
    
    printf("The swapped values a: %d and b: %d", a, b);
    
    return 0;
}

Output:

Enter a: 10
Enter b: 20
The swapped values a: 20 and b: 10

Note that the swapping using / and * will not work if one of the swapping values is zero (0).

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