zoukankan      html  css  js  c++  java
  • HDU 4405 Aeroplane chess(概率DP求期望)

    Aeroplane chess

    Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
    Total Submission(s): 361    Accepted Submission(s): 255


    Problem Description
    Hzz loves aeroplane chess very much. The chess map contains N+1 grids labeled from 0 to N. Hzz starts at grid 0. For each step he throws a dice(a dice have six faces with equal probability to face up and the numbers on the faces are 1,2,3,4,5,6). When Hzz is at grid i and the dice number is x, he will moves to grid i+x. Hzz finishes the game when i+x is equal to or greater than N.

    There are also M flight lines on the chess map. The i-th flight line can help Hzz fly from grid Xi to Yi (0<Xi<Yi<=N) without throwing the dice. If there is another flight line from Yi, Hzz can take the flight line continuously. It is granted that there is no two or more flight lines start from the same grid.

    Please help Hzz calculate the expected dice throwing times to finish the game.
     
    Input
    There are multiple test cases.
    Each test case contains several lines.
    The first line contains two integers N(1≤N≤100000) and M(0≤M≤1000).
    Then M lines follow, each line contains two integers Xi,Yi(1≤Xi<Yi≤N).  
    The input end with N=0, M=0.
     
    Output
    For each test case in the input, you should output a line indicating the expected dice throwing times. Output should be rounded to 4 digits after decimal point.
     
    Sample Input
    2 0 8 3 2 4 4 5 7 8 0 0
     
    Sample Output
    1.1667 2.3441
     
    Source
     
    Recommend
    zhoujiaqi2010
     
     
    网赛时很简单的概率dp的题目。那个时候不会概率dp,没有做过概率dp太弱了~~~~~~~
    /*
    
    概率DP求期望。
    形成一个有向无环图。按照公式递推就可以了。
    dp[i]表示i点跳到目标状态的期望步数
    
    */
    
    
    #include<stdio.h>
    #include<iostream>
    #include<algorithm>
    #include<string.h>
    #include<vector>
    using namespace std;
    
    const int MAXN=100010;
    double dp[MAXN];
    vector<int>vec[MAXN];
    bool used[MAXN];
    int main()
    {
        int n,m;
        int u,v;
        while(scanf("%d%d",&n,&m))
        {
            if(n==0&&m==0)break;
            for(int i=0;i<=n;i++)vec[i].clear();
            memset(dp,0,sizeof(dp));
            while(m--)
            {
                scanf("%d%d",&u,&v);
                vec[v].push_back(u);
            }
            memset(used,false,sizeof(used));
            for(int i=0;i<vec[n].size();i++)
            {
                v=vec[n][i];
                dp[v]=0;
                used[v]=true;
            }
            for(int i=n-1;i>=0;i--)
            {
                if(used[i]==false)
                {
                    for(int j=i+1;j<=i+6;j++)dp[i]+=dp[j]/6;
                    dp[i]+=1;
                    used[i]=true;
                }
    
                for(int j=0;j<vec[i].size();j++)
                {
                    v=vec[i][j];
                    dp[v]=dp[i];
                    used[v]=true;
                }
            }
            printf("%.4lf\n",dp[0]);
        }
        return 0;
    }
    人一我百!人十我万!永不放弃~~~怀着自信的心,去追逐梦想
  • 相关阅读:
    Spring Boot -- Spring Boot之@Async异步调用、Mybatis、事务管理等
    Spring Boot -- 认识Spring Boot
    大数据 -- Cloudera Manager(简称CM)+CDH构建大数据平台
    大数据 -- kafka学习笔记:知识点整理(部分转载)
    大数据 -- Hadoop集群环境搭建
    大数据 -- zookeeper和kafka集群环境搭建
    Java基础 -- 数组
    sbt spark2.3.1 idea打包Caused by: java.lang.ClassNotFoundException: scala.Product$class
    windows 安装python pip Could not install packages due to anEnvironmentError: [WinError 5] 拒绝访问
    博客园编辑数学公式的方法
  • 原文地址:https://www.cnblogs.com/kuangbin/p/2710976.html
Copyright © 2011-2022 走看看