CF1304E.1-Trees and Queries
普及+/提高
通过率:0%
时间限制:4.00s
内存限制:512MB
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题目描述
Gildong was hiking a mountain, walking by millions of trees. Inspired by them, he suddenly came up with an interesting idea for trees in data structures: What if we add another edge in a tree?
Then he found that such tree-like graphs are called 1-trees. Since Gildong was bored of solving too many tree problems, he wanted to see if similar techniques in trees can be used in 1-trees as well. Instead of solving it by himself, he's going to test you by providing queries on 1-trees.
First, he'll provide you a tree (not 1-tree) with n vertices, then he will ask you q queries. Each query contains 5 integers: x, y, a, b, and k. This means you're asked to determine if there exists a path from vertex a to b that contains exactly k edges after adding a bidirectional edge between vertices x and y. A path can contain the same vertices and same edges multiple times. All queries are independent of each other; i.e. the added edge in a query is removed in the next query.
吉隆在爬山时,穿行于成千上万棵树木之间。受此启发,他突然想到数据结构中“树”的一个有趣变体:如果我们在一棵树中再额外添加一条边,会怎样?
随后他发现,这类类似树的图被称为1-树(1-tree)。由于吉隆已厌倦了解太多关于树的问题,他想检验一下:解决树问题的类似技巧是否也能用于1-树?但他并不打算自己动手求解,而是准备通过一系列关于1-树的查询来考验你。
首先,他会给你一棵含 n 个顶点的普通树(不是1-树);接着,他会向你提出 q 个查询。每个查询包含 5 个整数:x、y、a、b 和 k。其含义是:在顶点 x 与 y 之间添加一条双向边后,判断是否存在一条从顶点 a 到 b 的路径,且该路径恰好包含 k 条边。路径允许重复经过同一顶点和同一条边。所有查询相互独立;即某次查询中添加的边,在下一次查询中即被移除。
输入格式
The first line contains an integer n (3≤n≤105), the number of vertices of the tree.
Next n−1 lines contain two integers u and v (1≤u,v≤n, u=v) each, which means there is an edge between vertex u and v. All edges are bidirectional and distinct.
Next line contains an integer q (1≤q≤105), the number of queries Gildong wants to ask.
Next q lines contain five integers x, y, a, b, and k each (1≤x,y,a,b≤n, x=y, 1≤k≤109) – the integers explained in the description. It is guaranteed that the edge between x and y does not exist in the original tree.
第一行包含一个整数 n(3≤n≤105),表示树的顶点数。
接下来 n−1 行,每行包含两个整数 u 和 v(1≤u,v≤n,u=v),表示顶点 u 与 v 之间存在一条边。所有边均为无向且互不相同。
下一行包含一个整数 q(1≤q≤105),表示 Gildong 想要询问的查询次数。
接下来 q 行,每行包含五个整数 x、y、a、b 和 k(1≤x,y,a,b≤n,x=y,1≤k≤109),其含义如题面描述所述。保证原树中不存在连接 x 与 y 的边。
输出格式
For each query, print "YES" if there exists a path that contains exactly k edges from vertex a to b after adding an edge between vertices x and y. Otherwise, print "NO".
You can print each letter in any case (upper or lower).
对于每个查询,如果在顶点 x 和 y 之间添加一条边后,存在一条从顶点 a 到 b、恰好包含 k 条边的路径,则输出 "YES";否则输出 "NO"。
你可以以任意大小写(大写或小写)输出每个字母。
输入输出样例
输入#1
5 1 2 2 3 3 4 4 5 5 1 3 1 2 2 1 4 1 3 2 1 4 1 3 3 4 2 3 3 9 5 2 3 3 9
输出#1
YES YES NO YES NO
说明/提示
The image below describes the tree (circles and solid lines) and the added edges for each query (dotted lines).

Possible paths for the queries with "YES" answers are:
- 1-st query: 1 – 3 – 2
- 2-nd query: 1 – 2 – 3
- 4-th query: 3 – 4 – 2 – 3 – 4 – 2 – 3 – 4 – 2 – 3
下图描述了树(圆圈和实线)以及每次查询所添加的边(虚线)。

答案为 “YES” 的查询所对应的可能路径如下:
- 第 1 次查询:1 – 3 – 2
- 第 2 次查询:1 – 2 – 3
- 第 4 次查询:3 – 4 – 2 – 3 – 4 – 2 – 3 – 4 – 2 – 3
输入解题思路,AI测评打分。不知道怎么写?