Swapping Two Numbers Without Using Third Number

program:

#include<stdio.h>

int main()

{

int a=10,b=20;

printf("Before swapping a=%d and b=%d\n",a,b);

a=a+b;

b=a-b;

a=a-b;

printf("After swapping a=%d and b=%d\n",a,b);

}

output: