A simple algorithm for calculating the binomial coefficient written i C++.

choose.cpp

#include <iostream>

int choose(int n, int k)
{
  if(k > n)
    return -1;
  else if(k > n - k)
    return choose(n, n - k);
  else if(k == 1)
    return n;
  else
    return (choose(n, k - 1) * (n - k + 1)) / k;
}

int main()
{
  std::cout << choose(500, 4) << std::endl;
  return 0;
}