[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;}