Swap two numbers without using third variable in C

In this post, you will learn different ways for swapping two numbers using C programming language. Such a type of question is generally asked in programming interviews, the interviewer may ask to write a program for swapping of two numbers using a particular way.

C Swap two numbers without using temporary variable

In the given C program, we ask the user to enter two integer values and store them in two variables. Then, we swap the entered value using the addition and subtraction operators.

#include<stdio.h>  
int main()   
{   
  int x, y;  
  printf("Enter the value of x and y: ");  
  scanf("%d %d",&x,&y);  
  printf("Before swapping: %d   %d\n",x,y);  
  
  /*Swapping in steps  */
  x = x + y;   
  y = x - y;    
  x = x - y;  
  
  /*Verifying swapped values  */
  printf("After swapping: %d    %d",x,y);   
  return 0;   
}

Output of the above code:

Enter the value of x and y: 200 150
Before swapping: 200   150
After swapping: 150    200

C Swap two numbers using Multiplication and division

In the given C program, we swap two numbers using the arithmetic operators multiplication and division.

// C program to swap two variables
#include <stdio.h>
  
int main()   
{   
   int x, y;  
   printf("Enter the value of x and y: ");  
   scanf("%d %d",&x,&y);  
   printf("Before swapping: %d   %d\n",x,y);  
  
    // swapping 'x' and 'y' using 
    // multiplication and division
        
    x = x * y; 
    y = x / y; 
    x = x / y; 
  
    // Verifying swapped values  
    printf("After swapping: %d    %d",x,y);   
    return 0;   
}

Output of the above code:

Enter the value of x and y: 200 150
Before swapping: 200   150
After swapping: 150    200

C program to swap two numbers using Bitwise XOR

Here, we have used the bitwise XOR operator to swap two variables. The XOR of two numbers x and y returns a number that has all the bits as 1 wherever bits of x and y differ. For example, XOR of 10 (binary 1010) and 5 (binary 0101) is 1111.

#include <stdio.h>
int main()
{
    int x = 40, y = 55;
    printf("Before swapping: x = %d, y = %d", x, y);   
    x = x ^ y;
    y = x ^ y;
    x = x ^ y;
 
    printf("\nAfter Swapping: x = %d, y = %d", x, y);
    return 0;
}

Output of the above code:

Before swapping: x = 40, y = 55
After Swapping: x = 55, y = 40

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