xor swap trick
/* swap.c
*
* the xor swap trick
*
* Usage:
* $ ./swap
* before swap: x=1234, y=4792
* after swap : x=4792, y=1234
* or
* $ ./swap 823 101
* before swap: x=823, y=101
* after swap : x=101, y=823
* or
* $ ./swap 1 2 verbose
* address of x is 0xbfc0fcdc
* address of y is 0xbfc0fcd8
* before swap: x=1, y=2
* after swap: x=2, y=1
*
* This is explained on wikipedia's 'XOR swap algorithm' page.
*/
#include <stdio.h>
void swap(int* xp, int* yp){
*xp = *xp ^ *yp; // Effectively it looks like this:
*yp = *xp ^ *yp; // y_new = (x ^ y) ^ y
*xp = *xp ^ *yp; // x_new = (x ^ y) ^ (x ^ y ^ y)
}
int main(int argc, char* argv[]){
int x = 1234;
int y = 4792;
if (argc >= 3){
sscanf(argv[1], "%d", &x);
sscanf(argv[2], "%d", &y);
}
if (argc >= 4){
printf("address of x is %p \n", (void*) &x);
printf("address of y is %p \n", (void*) &y);
}
printf("before swap: x=%i, y=%i \n", x, y);
swap(&x, &y);
printf("after swap : x=%i, y=%i \n", x, y);
return 0;
}
