C Program to Swap Two Numbers

Code of the Program

#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

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

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