#include <stdio.h>
#include <stdlib.h>

/* swap i elements of the arrays xs and ys */
void swap (int xs[], int ys[], int i) {
    
  int tmp;
  i--;
  while (i >= 0) {
      
    tmp = xs[i];
    xs[i] = ys[i];
    ys[i] = tmp;
    i--;
  }
}


int main () {
  
  int xs[10];
  int ys[10];

  int i;


  /* initialise the array */


  for (i = 0; i < 10; i++) {
    xs[i] = 2*i;
    ys[i] = 2*i + 1;
  }

  
  /* swap the elements */
  swap (xs, ys, 10);
  

  /* print the result */
  for (i = 0; i< 10; i++) {
    
    printf ("xs[%d] = %d, ys[%d] = %d\n", i, xs[i], i, ys[i]);
  }

  exit (0);
}