#include <iostream>
#include <cstdlib>
#include <cstdio>

void swap_if(int & x, int & y)
{ if (x > y)
  { int temp = x;
    x = y;
    y = temp; } }

void main(int argc, char * argv[])
                  /* If I run the program by typing  a.out 15
                     argv[0] will be "a.out"
                     argv[1] will be "15"
                     argv[2] will be NULL
                     argc    will be 2         */
{ srandomdev();
  const int N = atol(argv[1]);     // atol : convert ascii string of digits to int
  int A[1000];

  for (int i = 0; i < N; i += 1)
    A[i] = random() % 1000;

  printf("before:\n ");
  for (int i = 0; i < N; i += 1)
    printf(" %3d", A[i]);
  printf("\n");

/* This is the original triangle of bricks

  swap_if(a, b); swap_if(b, c); swap_if(c, d); swap_if(d, e); swap_if(e, f);
  swap_if(a, b); swap_if(b, c); swap_if(c, d); swap_if(d, e);
  swap_if(a, b); swap_if(b, c); swap_if(c, d);
  swap_if(a, b); swap_if(b, c);
  swap_if(a, b); swap_if(b, c);
  swap_if(a, b);

    Now we'll convert it into a little loop */

  for (int stop = N-1; stop > 0; stop -= 1)
    for (int first = 0; first < stop ; first += 1)
      swap_if(A[first], A[first+1]);

  printf("after:\n ");
  for (int i = 0; i < N; i += 1)
    printf(" %3d", A[i]);
  printf("\n");

}