#include <stdio.h>
#define SIZE 5
void swap(int [], int);
void disp(int [], int);

int main(void) {
  int arr[SIZE] = {1,2,3,-9,0};

  disp(arr, SIZE);
  swap(arr, SIZE);
  printf("\n====================\n\n");
  disp(arr, SIZE);
  return 0;
}

/*======= swap declaration =======*/
void swap(int arr[], int size) {
  for (int i = 0; i < size/2; i++) {
    arr[i] = arr[i] - arr[size - 1 - i];
    arr[size - 1 - i] = arr[i] + arr[size - 1 - i];
    arr[i] = arr[size - 1 - i] - arr[i];
  }
}
/*======= disp declaration =======*/
void disp(int arr[], int size) {
  for (int i = 0; i < size; i++) {
    printf("arr[%d] = %d\n", i, arr[i]);
  }
}