A丢100个6面骰子，B丢160个4面骰子。那么A的点数总和比B的点数总和大的几率以及相等的几率分别该怎么计算？ http://weibo.com/2039631434/zaMYL2jOj

pab.cpp

/*
A丢100个6面骰子，B丢160个4面骰子。那么A的点数总和比B的点数总和大的几率以及相等的几率分别该怎么计算？
http://weibo.com/2039631434/zaMYL2jOj
*/
#include <cstdio>
#include <cassert>

template<int n,int dice>
double f(int d)
{
  static double fn[n+1][n*dice+1] = {0};
  static bool inited = false;
  if (!inited)
  {
    fn[0][0] = 1;
    for (int j = 1; j <= n; j++)
    {
      for (int i = j; i <= j*dice; i++)
      {
        double p = 0;
        for (int k = 1; k <= dice; k++)
        {
          if (i >= k)
            p += fn[j-1][i - k] / (double)dice;
        }
        fn[j][i] = p;
      }
    }
    inited = true;
  }
  assert(d <= n*dice+1);
  return fn[n][d];
}

double p_equal()
{
  double p = 0;
  for (int d = 160; d <= 600; d++)
  {
    p += f<100, 6>(d) * f<160, 4>(d);
  }
  return p;
}

double p_6_gt_4()
{
  double p = 0;
  for (int a = 161; a <= 600; a++)
  {
    for (int b = 160; b < a; b++)
    {
      p += f<100, 6>(a) * f<160, 4>(b);
    }
  }  
  return p;
}

int main()
{
  printf("%lf\n%lf\n", p_equal(), p_6_gt_4());
  return 0;
}