CF1714F.Build a Tree and That Is It
普及+/提高
通过率:0%
时间限制:2.00s
内存限制:256MB
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题目描述
A tree is a connected undirected graph without cycles. Note that in this problem, we are talking about not rooted trees.
You are given four positive integers n,d12,d23 and d31. Construct a tree such that:
- it contains n vertices numbered from 1 to n,
- the distance (length of the shortest path) from vertex 1 to vertex 2 is d12,
- distance from vertex 2 to vertex 3 is d23,
- the distance from vertex 3 to vertex 1 is d31.
Output any tree that satisfies all the requirements above, or determine that no such tree exists.
树是一个无环的连通无向图。注意,在本题中,我们讨论的是非有根树(即不指定根节点的树)。
给定四个正整数 n,d12,d23 和 d31。请构造一棵满足以下条件的树:
- 该树包含 n 个顶点,编号为 1 到 n;
- 顶点 1 到顶点 2 的距离(即最短路径的长度)为 d12;
- 顶点 2 到顶点 3 的距离为 d23;
- 顶点 3 到顶点 1 的距离为 d31。
输出任意一棵满足上述所有条件的树;若不存在这样的树,则判定其不存在。
输入格式
The first line of the input contains an integer t (1≤t≤104) —the number of test cases in the test.
This is followed by t test cases, each written on a separate line.
Each test case consists of four positive integers n,d12,d23 and d31 (3≤n≤2⋅105;1≤d12,d23,d31≤n−1).
It is guaranteed that the sum of n values for all test cases does not exceed 2⋅105.
输入的第一行包含一个整数 t(1≤t≤104),表示测试用例的数量。
接下来是 t 个测试用例,每个测试用例占单独一行。
每个测试用例包含四个正整数 n,d12,d23 和 d31(3≤n≤2⋅105;1≤d12,d23,d31≤n−1)。
保证所有测试用例的 n 值之和不超过 2⋅105。
输出格式
For each test case, print YES if the suitable tree exists, and NO otherwise.
If the answer is positive, print another n−1 line each containing a description of an edge of the tree — a pair of positive integers xi,yi, which means that the ith edge connects vertices xi and yi.
The edges and vertices of the edges can be printed in any order. If there are several suitable trees, output any of them.
对于每个测试用例,如果存在满足条件的树,则输出 YES;否则输出 NO。
如果答案为 YES,则再输出 n−1 行,每行描述树中的一条边——即一对正整数 xi,yi,表示第 i 条边连接顶点 xi 和 yi。
边及其顶点的输出顺序可以任意。如果存在多个满足条件的树,输出任意一个即可。
输入输出样例
输入#1
9 5 1 2 1 5 2 2 2 5 2 2 3 5 2 2 4 5 3 2 3 4 2 1 1 4 3 1 1 4 1 2 3 7 1 4 1
输出#1
YES 1 2 4 1 3 1 2 5 YES 4 3 2 5 1 5 5 3 NO YES 2 4 4 1 2 5 5 3 YES 5 4 4 1 2 5 3 5 YES 2 3 3 4 1 3 NO YES 4 3 1 2 2 4 NO
输入解题思路,AI测评打分。不知道怎么写?