#include <stdio.h>

void swap(int*, int*);

int main(void)
{
   int i = 100, j = 500;
   int *p1 = &i, *p2 = &j;
   printf("%d %d %p %p\n", i, j, p1, p2);
   swap(p1, p2);
   printf("%d %d %p %p\n", i, j, p1, p2);
   
   return 0;
}

void swap(int *px, int *py) {
   int temp = *px;
   *px = *py;
   *py = temp;
   px = py = NULL;
}