[题解]CF611H New Year and Forgotten Tree 神题了... 题目描述 给定你一棵树,可是每个节点上的编号看不清了,只能辨别它的长度.现在用问号的个数代表每个节点编号那个数字的长度,请你还原这一颗树,任意输出一个方案,有PSJ\(SPJ\)来检验你的正确性.无解输出一行\(-1\) . 输入格式: 第一行一个整数\(n\). 接下来 \(n-1\)行每行两个有问号构成的字符串,代表编号长度. 输出格式 : 若有解,直接输出\(n-1\)行,每行两个正整数,代表你还原…

首先,来构造这棵树的形态 称位数相同的点为一类点,从每一类点中任选一个点,具有以下性质: 1.每一类中选出的点的导出子图连通(是一颗树) 2.每一条边必然有一个端点属于某一类中选出的点 (关于"若有解,一定存在上述这种形式的解"的证明可能比较困难,大概感性理解一下?) 由于类别很少(记为$m=\lfloor\log_{10}n\rfloor+1$),$o(m^{m-2})$或$o{\frac{(m+1)m}{2}\choose m-1}$暴力确定这$m$类点中选出的点的树形态(实际差不…

C. Bear and Forgotten Tree 3 题目连接: http://www.codeforces.com/contest/658/problem/C Description A tree is a connected undirected graph consisting of n vertices and n  -  1 edges. Vertices are numbered 1 through n. Limak is a little polar bear and Rade…

E. Bear and Forgotten Tree 2 题目连接: http://www.codeforces.com/contest/653/problem/E Description A tree is a connected undirected graph consisting of n vertices and n  -  1 edges. Vertices are numbered 1 through n. Limak is a little polar bear. He once…

E - Bear and Forgotten Tree 2 思路:先不考虑1这个点,求有多少个连通块,每个连通块里有多少个点能和1连,这样就能确定1的度数的上下界. 求连通块用链表维护. #include<bits/stdc++.h> #define LL long long #define fi first #define se second #define mk make_pair #define PII pair<int, int> #define PLI pair<L…

B. Bear and Forgotten Tree 3 time limit per test2 seconds memory limit per test256 megabytes inputstandard input outputstandard output A tree is a connected undirected graph consisting of n vertices and n  -  1 edges. Vertices are numbered 1 through…

Bear and Forgotten Tree 3 time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output A tree is a connected undirected graph consisting of n vertices and n  -  1 edges. Vertices are numbered 1 through…

题目链接: C. Bear and Forgotten Tree 3 time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output A tree is a connected undirected graph consisting of n vertices and n  -  1 edges. Vertices are numbered …

C. Bear and Forgotten Tree 3 time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output A tree is a connected undirected graph consisting of n vertices and n  -  1 edges. Vertices are numbered 1 thro…

Solution 提供一种新思路. 首先考虑如何判断一个状态是否合法. 考虑把所有十进制长度一样的数缩成一个点. 这样的点的个数 \(\le 5\). 蒟蒻猜了一个结论:只要满足对于所有缩出来的点的子集的点的个数 > 子集内边的个数,那么就是有解的. 这时 \(\tt \color{black}{S}\color{red}{egmentTree}\) 会下凡告诉你:这是对的!卡不掉! 但是这样只能判断可不可行啊,不能输出方案啊... 发现这个东西判断的时间复杂度很小,可以多次判断. 那么我们可以…