zoukankan      html  css  js  c++  java
  • luogu P3116 [USACO15JAN]会议时间Meeting Time

    题目描述

    Bessie and her sister Elsie want to travel from the barn to their favorite field, such that they leave at exactly the same time from the barn, and also arrive at exactly the same time at their favorite field.

    The farm is a collection of N fields (1 <= N <= 100) numbered 1..N, where field 1 contains the barn and field N is the favorite field. The farm is built on the side of a hill, with field X being higher in elevation than field Y if X < Y. An assortment of M paths connect pairs of fields. However, since each path is rather steep, it can only be followed in a downhill direction. For example, a path

    connecting field 5 with field 8 could be followed in the 5 -> 8 direction but not the other way, since this would be uphill. Each pair of fields is connected by at most one path, so M <= N(N-1)/2.

    It might take Bessie and Elsie different amounts of time to follow a path; for example, Bessie might take 10 units of time, and Elsie 20. Moreover, Bessie and Elsie only consume time when traveling on paths between fields -- since they are in a hurry, they always travel through a field in essentially zero time, never waiting around anywhere.

    Please help determine the shortest amount of time Bessie and Elsie must take in order to reach their favorite field at exactly the same moment.

    给出一个n个点m条边的有向无环图,每条边两个边权。

    n<=100,没有重边。

    然后要求两条长度相同且尽量短的路径,

    路径1采用第一种边权,路径2采用第二种边权。

    没有则输出”IMPOSSIBLE”

    输入输出格式

    输入格式:

    INPUT: (file meeting.in)

    The first input line contains N and M, separated by a space.

    Each of the following M lines describes a path using four integers A B C D, where A and B (with A < B) are the fields connected by the path, C is the time required for Bessie to follow the path, and D is the time required for Elsie to follow the path. Both C and D are in the range 1..100.

    输出格式:

    OUTPUT (file meeting.out)

    A single integer, giving the minimum time required for Bessie and

    Elsie to travel to their favorite field and arrive at the same moment.

    If this is impossible, or if there is no way for Bessie or Elsie to reach

    the favorite field at all, output the word IMPOSSIBLE on a single line.

    输入输出样例

    输入样例#1:
    3 3 
    1 3 1 2 
    1 2 1 2 
    2 3 1 2 
    
    输出样例#1:
    2 

    说明

    SOLUTION NOTES:

    Bessie is twice as fast as Elsie on each path, but if Bessie takes the

    path 1->2->3 and Elsie takes the path 1->3 they will arrive at the

    same time.

  • 相关阅读:
    用户添加到sudoer列表## Allow root to run any commands anywhere root ALL=(ALL) ALL Iron ALL=(ALL) ALL
    Linux下script命令录制、回放和共享终端操作script -t 2> timing.log -a output.session # 开始录制
    解决nohup: 忽略输入并把输出追加到"nohup.out"或者nohup: 忽略输入重定向错误到标准输出端
    grub救援模式
    如何讓RHEL7/CentOS7開機過程顯示更多資訊
    CSAPP读书随笔之一:为什么汇编器会将call指令中的引用的初始值设置为-4
    对angular实现延迟加载template和controller
    angularjs+jasmine单元测试入门
    设计模式简单工厂之我见
    融云官方cordova示例使用指南
  • 原文地址:https://www.cnblogs.com/sssy/p/7152514.html
Copyright © 2011-2022 走看看