数据结构练习（32）n个骰子的点数

http://zhedahht.blog.163.com/blog/static/254111742009101524946359/

思路：

简单的动态规划，利用滚动数组会节省内存。

#include <iostream>

#include <cmath>

using namespace std;



const int MAX_VALUE = 6;



void SolveProbability(int n)

{

    int* dp[2];

    int maxd = n * MAX_VALUE + 1;

    dp[0] = new int[maxd];

    dp[1] = new int[maxd];



    for (int i = 0; i < maxd; ++i)

        dp[0][i] = dp[1][i] = 0;



    int flag = 0;

    dp[0][0] = 1;



    for (int i = 1; i <= n; ++i)

    {

        for (int j = 0; j < maxd; ++j)

        {

            dp[1-flag][j] = 0;

            for (int k = 1; k <= j && k <= MAX_VALUE; ++k)

                    dp[1-flag][j] += dp[flag][j-k];

        }

        flag = 1 - flag;

    }



    double total = pow((double)MAX_VALUE, n);



    for (int i = n; i < maxd; ++i)

    {

        if (dp[flag][i])

        {

            double ratio = (double)dp[flag][i] / total;

            cout << i << ": " << ratio << endl;

        }

    }

    delete[] dp[0];

    delete[] dp[1];

}



int main()

{

    SolveProbability(2);

    return 0;

}