#P2982. [USACO10FEB] Slowing down G
[USACO10FEB] Slowing down G
题目描述
Every day each of Farmer John's N cows conveniently numbered move from the barn to her private pasture. The pastures are organized as a tree, with the barn being on pasture . Exactly cow unidirectional paths connect the pastures; directly connected pastures have exactly one path. Path connects pastures and .
Cow has a private pasture . The barn's small door lets only one cow exit at a time; and the patient cows wait until their predecessor arrives at her private pasture. First cow exits and moves to pasture . Then cow exits and goes to pasture , and so on.
While cow walks to she might or might not pass through a pasture that already contains an eating cow. When a cow is present in a pasture, cow walks slower than usual to prevent annoying her friend.
FJ would like to know how many times each cow has to slow down.
每天 Farmer John 的 头奶牛,编号 ,从粮仓走向他的自己的牧场。牧场构成了一棵树,粮仓在 号牧场。恰好有 条道路直接连接着牧场,使得牧场之间都恰好有一条路径相连。第 条路连接着 和 。奶牛们每人有一个私人牧场 。粮仓的门每次只能让一只奶牛离开。耐心的奶牛们会等到他们的前面的朋友们到达了自己的私人牧场后才离开。首先奶牛 离开,前往 ;然后是奶牛 ,以此类推。
当奶牛 走向牧场 的时候,他可能会经过正在吃草的同伴旁。当路过已经有奶牛的牧场时,奶牛 会放慢自己的速度,防止打扰他的朋友。
FJ 想要知道奶牛们总共要放慢多少次速度。
输入格式
* Line : Line contains a single integer:
* Lines : Line contains two space-separated integers: and
* Lines : line contains a single integer:
第一行:有一个整数 。
第 行:第 行有两个以空格隔开的整数 和 。
第 行:第 行有一个整数 。
输出格式
* Lines :Line contains the number of times cow has to slow down.
第 行:第 行包括奶牛 需要放慢速度的次数。
提示
数据范围:。