zoukankan      html  css  js  c++  java
  • HDU 4405 概率DP

                                             Aeroplane chess

                                      Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)


    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
     
    题解:dp[i]表示出去的期望,逆推就是了
    //1085422276
    #include<iostream>
    #include<cstdio>
    #include<cstring>
    #include<string>
    #include<algorithm>
    #include<queue>
    #include<cmath>
    #include<map>
    #include<bitset>
    #include<set>
    #include<vector>
    using namespace std ;
    typedef long long ll;
    #define mem(a) memset(a,0,sizeof(a))
    #define meminf(a) memset(a,127,sizeof(a));
    #define memfy(a) memset(a,-1,sizeof(a))
    #define TS printf("111111
    ");
    #define FOR(i,a,b) for( int i=a;i<=b;i++)
    #define FORJ(i,a,b) for(int i=a;i>=b;i--)
    #define READ(a,b) scanf("%d%d",&a,&b)
    #define mod 1000000007
    #define maxn 100000+5
    inline ll read()
    {
        ll x=0,f=1;
        char ch=getchar();
        while(ch<'0'||ch>'9')
        {
            if(ch=='-')f=-1;
            ch=getchar();
        }
        while(ch>='0'&&ch<='9')
        {
            x=x*10+ch-'0';
            ch=getchar();
        }
        return x*f;
    }
    //****************************************
    int n,m;
    double dp[maxn];
    int ne[maxn];
    int main()
    {
    
        while(READ(n,m)!=EOF)
        {  mem(dp);memfy(ne);
        int x,y;
            if(n==0&&m==0)break;
            FOR(i,1,m)
            {
                scanf("%d%d",&x,&y);
                ne[x]=y;
            }
            FORJ(i,n-1,0)
            {
                if(ne[i]!=-1)dp[i]=dp[ne[i]];
                else {
                    FOR(l,1,6)dp[i]+=(dp[i+l]/6.0);
                    dp[i]+=1.0;
                }
            }
            printf("%.4f
    ",dp[0]);
        }
        return 0;
    }
    代码
  • 相关阅读:
    day28-描述符应用与类的装饰器
    MySQL-快速入门(8)存储过程、存储函数
    MySQL-快速入门(7)索引
    MySQL-快速入门(6)连接查询、子查询、正则表达式查询、数据的插入删除更新
    MySQL-快速入门(5)数据查询-常用关键字、分组查询、聚合函数
    MySQL-快速入门(4)MySQL函数
    MySQL-快速入门(3)运算符
    MySQL-快速入门(2)数据类型
    MySQL-快速入门(1)基本数据库、表操作语句
    MySql-Mysql技术内幕~SQL编程学习笔记(N)
  • 原文地址:https://www.cnblogs.com/zxhl/p/4811055.html
Copyright © 2011-2022 走看看