zoj 3640 Help Me Escape 概率DP

记忆化搜索+概率DP

代码如下：

 

 1 #include<iostream>

 2 #include<stdio.h>

 3 #include<algorithm>

 4 #include<iomanip>

 5 #include<cmath>

 6 #include<cstring>

 7 #include<vector>

 8 #define ll __int64

 9 #define pi acos(-1.0)

10 #define MAX 50000

11 using namespace std;

12 int c[101],n,ff;

13 double dp[100001];

14 double solve(int f)

15 {

16     if(dp[f]>0) return dp[f];

17     dp[f]=0;

18     for(int i=0;i<n;i++){

19         if(f>c[i]){

20             double t=(sqrt(5.0)+1.0)/2*c[i]*c[i];

21             int p=(int)t;

22             dp[f]+=1.0*p/n;

23         }

24         else{

25             dp[f]+=(1+solve(f+c[i]))/n;

26         }

27     }

28     return dp[f];

29 }

30 int main(){

31     while(scanf("%d%d",&n,&ff)!=EOF){

32         for(int i=0;i<n;i++) cin>>c[i];

33         memset(dp,0,sizeof(dp));

34         printf("%.3lf\n",solve(ff));

35     }

36 

37     return 0;

38 }

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