[hdu4815]Little Tiger vs. Deep Monkey

概率DP，长春现场赛的题，当时没看，现在补上...

f[i][j]代表答对前i道题得j分的概率

转移方程f[i][j]+=f[i-1][j]/2;f[i][j+a[i]]+=f[i-1][j]/2; a[i]是第i道题的分数

#include <iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int T,a[40010],n;
double p,f[50][40010];
int main()
{
    scanf("%d",&T);
    for(int Ti=1;Ti<=T;Ti++)
    {
        scanf("%d %lf",&n,&p);
        for (int i=1;i<=n;i++)
        scanf("%d",&a[i]);
        memset(f,0,sizeof(f));
        f[0][0]=1;
        for(int i=1;i<=n;i++)
        {
            for (int j=0;j<=40000-a[i];j++)
            {
                f[i][j]+=f[i-1][j]/2;
                f[i][j+a[i]]+=f[i-1][j]/2;
            }
        }
        double t=0;
        int ans=0;
        for(int i=0;i<=40000;i++)
        {
            if (t<p) {t+=f[n][i];ans=i;} else break;
        }
        printf("%d\n",ans);
    }
    return 0;
}