zoukankan      html  css  js  c++  java
  • poj2391 最大流+拆点+二分答案+Floyd

    Ombrophobic Bovines
    Time Limit: 1000MS   Memory Limit: 65536K
    Total Submissions: 19553   Accepted: 4217

    Description

    FJ's cows really hate getting wet so much that the mere thought of getting caught in the rain makes them shake in their hooves. They have decided to put a rain siren on the farm to let them know when rain is approaching. They intend to create a rain evacuation plan so that all the cows can get to shelter before the rain begins. Weather forecasting is not always correct, though. In order to minimize false alarms, they want to sound the siren as late as possible while still giving enough time for all the cows to get to some shelter.

    The farm has F (1 <= F <= 200) fields on which the cows graze. A set of P (1 <= P <= 1500) paths connects them. The paths are wide, so that any number of cows can traverse a path in either direction.

    Some of the farm's fields have rain shelters under which the cows can shield themselves. These shelters are of limited size, so a single shelter might not be able to hold all the cows. Fields are small compared to the paths and require no time for cows to traverse.

    Compute the minimum amount of time before rain starts that the siren must be sounded so that every cow can get to some shelter.

    Input

    * Line 1: Two space-separated integers: F and P

    * Lines 2..F+1: Two space-separated integers that describe a field. The first integer (range: 0..1000) is the number of cows in that field. The second integer (range: 0..1000) is the number of cows the shelter in that field can hold. Line i+1 describes field i.

    * Lines F+2..F+P+1: Three space-separated integers that describe a path. The first and second integers (both range 1..F) tell the fields connected by the path. The third integer (range: 1..1,000,000,000) is how long any cow takes to traverse it.

    Output

    * Line 1: The minimum amount of time required for all cows to get under a shelter, presuming they plan their routes optimally. If it not possible for the all the cows to get under a shelter, output "-1".

    Sample Input

    3 4
    7 2
    0 4
    2 6
    1 2 40
    3 2 70
    2 3 90
    1 3 120

    Sample Output

    110

    嗯。。解法rt
  • 相关阅读:
    java基础面试题:说说&和&&的区别
    java基础面试题:java中有没有goto? 在JAVA中如何跳出当前的多重嵌套循环?
    Java基础面试操作题: 获取 1-20 之间的随机数,共计 20 个,要求不能重复 获取 1-20 之间的随机数,共计 10 个,要求不能重
    Intellij设置Eclipse 快捷键
    Intellij 安装sonarlint
    Intellij 关闭参数提示
    Linux中Firefox——Firebug插件安装及使用
    Linux中Firefox——Httpfox插件安装及使用
    OpenCV——Haar-like特征
    Python学习笔记6(列表生成式)
  • 原文地址:https://www.cnblogs.com/mfys/p/7352026.html
Copyright © 2011-2022 走看看