// Monte-Carlo simulations
//
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

void shuffle( int a[], int n) { // put array into random order
  while( n > 1) {
    int i = rand() % n;  // random position 0 ... n-1
    --n;
    int t = a[i]; a[i] = a[n]; a[n] = t; // swap a[i] and a[n]
  }
}

int trial( void) //  return 1 for success, otherwise 0
{
  // int c = rand() % 2; // coin flip: 1 for heads, 0 for tails
  // return c;
  //
  // int d1 = rand() % 6 + 1, d2 = rand() % 6 + 1; // two 6-sided dice
  // if( d1 + d2 == 7) return 1;
  //
  // blackjack:
  int a[52]; for( int i = 0; i < 52; ++i) a[i] = i % 13 + 1; // 1 to 13, 4 times
  shuffle( a, 52);
  int c1 = a[0], c2 = a[1]; // first two cards, check Ace+Ten or Ten+Ace
  if( (c1 == 1 && c2 >= 10) || (c2 == 1 && c1 >= 10) ) return 1;
  return 0;
}

int main( void)
{
  srand(time(0));

  int n = 10000, count = 0; // number of trials, number of successes

  for( int i = 0; i < n; ++i) count += trial();
  
  double p = count/(double)n; // probability of success

  printf( "count = %i, trials = %i, p = %g\n", count, n, p);

  return 0;
}