Swap Two Numbers

In this example, you will learn to swap two numbers in C programming using two different techniques.

Swap Numbers Using Temporary Variable

    #include <stdio.h>
    int main() {
        double first, second, temp;
        printf("Enter first number: ");
        scanf("%lf", &first);
        printf("Enter second number: ");
        scanf("%lf", &second);

        // Value of first is assigned to temp
        temp = first;

        // Value of second is assigned to first
        first = second;

        // Value of temp (initial value of first) is assigned to second
        second = temp;

        printf("\nAfter swapping, firstNumber = %.2lf\n", first);
        printf("After swapping, secondNumber = %.2lf", second);
        return 0;
    }


                                    

Output

    Enter first number: 1.20
    Enter second number: 2.45
    
    After swapping, firstNumber = 2.45
    After swapping, secondNumber = 1.20

Explanation

In the this program, the temp variable is assigned the value of the first variable.

Then, the value of the first variable is assigned to the second variable.

Finally, the temp (which holds the initial value of first) is assigned to second. This completes the swapping process.

Swap Numbers Without Using Temporary Variables

    #include <stdio.h>
    int main() {
        double a, b;
        printf("Enter a: ");
        scanf("%lf", &a);
        printf("Enter b: ");
        scanf("%lf", &b);
    
        // Swapping
    
        // a = (initial_a - initial_b)
        a = a - b;   
     
        // b = (initial_a - initial_b) + initial_b = initial_a
        b = a + b;
    
        // a = initial_a - (initial_a - initial_b) = initial_b
        a = b - a;
    
        printf("After swapping, a = %.2lf\n", a);
        printf("After swapping, b = %.2lf", b);
        return 0;
    }


                                    

Output

    Enter a: 10.25
    Enter b: -12.5
    After swapping, a = -12.50
    After swapping, b = 10.25