How to swap two integers without using third variable

The safest way to swap two variables without using third variable is to use XOR operation as shown below.

This example C program swaps integer values of two variables i and j.

[neo@techpulp ~]# cat iswap.c
#include <stdio.h>

int main(int argc, char *argv[])
{
  int i = 10, j = 20;

  printf("Before swap: i = %d, j = %d\n", i, j);
  i = i^j;
  j = i^j;
  i = i^j;
  printf("After swap: i = %d, j = %d\n", i, j);
  return 0;
}
[neo@techpulp ~]# gcc iswap.c -o iswap
[neo@techpulp ~]# ./iswap
Before swap: i = 10, j = 20
After swap: i = 20, j = 10
[neo@techpulp ~]#

The same can be achieved using multiplication, division and subtraction operations bu they are not safe as integer overflow or underflow may occur.