zoj 3329 One Person Game 概率dp

题目链接：http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemCode=3329

参考网址：http://blog.csdn.net/morgan_xww/article/details/6775853

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
using namespace std;

const int maxn = 525;

double A[maxn],B[maxn];
int sta[maxn],icnt;
int n,k1,k2,k3,a,b,c;

int main()
{
    //freopen("E:\acm\input.txt","r",stdin);
    int T;
    cin>>T;
    while(T--){
        cin>>n>>k1>>k2>>k3>>a>>b>>c;
        icnt = 0;
        for(int i=1;i<=k1;i++)
            for(int j=1;j<=k2;j++)
                for(int k=1;k<=k3;k++)
                    if(i==a && j==b && k==c) continue;
                    else{
                        int sum = i + j + k;
                        sta[icnt++] = sum;
                    }

        for(int i=n+1;i<=maxn;i++)  A[i] = B[i] = 0;
        double p = 1.0/(k1*k2*k3);   //又犯傻了。
        for(int i=n;i>=0;i--){
            A[i] = 1 ;  B[i] = 0;
            for(int j=0;j<icnt;j++){
                A[i] += A[i+sta[j]];
                B[i] += B[i+sta[j]];
            }
            A[i] *= p;
            B[i] = p*B[i] + 1;
        }
        double ans = B[0]/(1-A[0]);
        printf("%.15lf
",ans);
    }
}