GCJ 2008 APAC local onsites C Millionaire

时间复杂度很大。dp[i][j]表示第i轮 j这种状态的概率。

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

double dp[][];
int T;
int M;
int X;
double P;

void work()
{
    memset(dp,,sizeof dp);
    dp[][<<M]=1.00;
    for(int r=; r<=M; r++)
    {
        for(int j=; j<=(<<M); j++)
        {
            double ans=;
            for(int k=;; k++)
            {
                if(j+k>(<<M)||j-k<) break;
                ans=max(ans,P*dp[r-][j+k]+(-P)*dp[r-][j-k]);
            }
            dp[r][j]=ans;
        }
    }
}

int main()
{
    //freopen("C-large-practice.in","r",stdin);
// freopen("C-large-practice.out","w",stdout);

    scanf("%d",&T);
    for(int Case=; Case<=T; Case++)
    {
        scanf("%d%lf%d",&M,&P,&X);
        work();
        long long XX=(long long)X;
        int d=(<<M);
        long long dd=(long long)d;
        long long RR=XX*dd/(long long);
        int R=int(RR);
        printf("Case #%d: %6lf\n",Case,dp[M][R]);
    }
    return ;
}