// The XOR swap trick is a classic bitwise technique that
// swaps two variables without using a temporary variable.
#include <stdio.h>
/**
* @brief Swap two integers using the XOR swap algorithm.
*
* The XOR swap algorithm exchanges two integer values without using
* a temporary variable.
*
* XOR properties used:
* x ^ x = 0
* x ^ 0 = x
* x ^ y ^ y = x
*
* WARNING:
* If both pointers reference the same memory location, the XOR algorithm
* would corrupt the value. Therefore, we explicitly guard against that case.
*
* @param a Pointer to the first integer.
* @param b Pointer to the second integer.
*/
void xor_swap(int *a, int *b)
{
if (a == NULL || b == NULL) {
return;
}
/* Prevent self-swap */
if (a == b) {
return;
}
*a ^= *b; /* 0101 ^ 1010 = 1111 = 15 */
*b ^= *a; /* 1010 ^ 1111 = 0101 = 5 */
*a ^= *b; /* 1111 ^ 0101 = 1010 = 10 */
}
int main(void)
{
int x = 5;
int y = 10;
printf("Before swap: x = %d, y = %d\n", x, y);
xor_swap(&x, &y);
printf("After swap: x = %d, y = %d\n", x, y);
return 0;
}
/*
run:
Before swap: x = 5, y = 10
After swap: x = 10, y = 5
*/
