Aizu - 2564 Tree Reconstruction 题意:一个有向图,要使得能确定每一条边的权值,要求是每个点的入权和出权相等,问你最少需要确定多少条边 思路:这题好像有一个定理之类的,对于每一个连通块,所需要的边数是 M-N(边数-点数) ,这个原理我还不是很清楚. 知道了这个之后,并查集求一下就完事了. 这题我大致看了一下官方 的提交记录,发现有好多种方法可以搞.23:48:40 #pragma comment(linker, "/STACK:1000000000")…

[BZOJ2959]长跑(Link-Cut Tree,并查集) 题面 BZOJ 题解 如果保证不出现环的话 妥妥的\(LCT\)傻逼题 现在可能会出现环 环有什么影响? 那就可以沿着环把所有点全部走一遍吧 所以,相当于把环看成一个点来搞一搞 所以,维护一个并查集 记录一下每个点被缩成了哪个点 然后再用\(LCT\)维护缩点后的树就行啦 #include<iostream> #include<cstdio> #include<cstdlib> #include<cs…

C. String Reconstruction 题目连接: http://codeforces.com/contest/828/problem/C Description Ivan had string s consisting of small English letters. However, his friend Julia decided to make fun of him and hid the string s. Ivan preferred making a new strin…

Description A tree is a well-known data structure that is either empty (null, void, nothing) or is a set of one or more nodes connected by directed edges between nodes satisfying the following properties. There is exactly one node, called the root, t…

Is It A Tree? 题目链接:http://poj.org/problem?id=1308 Description: A tree is a well-known data structure that is either empty (null, void, nothing) or is a set of one or more nodes connected by directed edges between nodes satisfying the following proper…

题目链接  Imbalance Value of a Tree 题意  给定一棵树.求树上所有简单路径中的最大权值与最小权值的差值的和. 首先考虑求所有简单路径中的最大权值和. 对所有点按照权值大小升序排序,即若$a[i] < a[j]$,那么$i$排在$j$前面. 接下来开始依次处理.对于每个点$i$,寻找周围跟他连通并且权值比他小的点进行合并,并且累加答案. 整个过程用并查集维护. 那么类似地,求最小权值的和的时候,我们把所有点权变成原来的相反数,再做一遍即可. #include <bit…

题目链接:http://codeforces.com/contest/828/problem/C C. String Reconstruction time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Ivan had string s consisting of small English letters. However, hi…

String Reconstruction Ivan had string s consisting of small English letters. However, his friend Julia decided to make fun of him and hid the string s. Ivan preferred making a new string to finding the old one. Ivan knows some information about the s…

#include <stdio.h> #include <string.h> ], g[]; int find(int x) //并查集的查找,找到共同的父亲 { if (f[x] != x) f[x] = find(f[x]); return f[x]; } int main() { ; while (scanf("%d%d", &a, &b) != EOF) { , t = ; && b<) break; ; i <…

Is It A Tree? Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 28838   Accepted: 9843 ->  Link  poj  <- ->  Link  hdu<- ->  Link  NYoj <- 这三个题题目都是一样的,我先做的NYOJ上的,以-1.-1结尾,然后跑到HDu上交一遍跪了,改成同时小于0就A了, 又到POJ上交一遍又跪了,改成-1.-1结尾又A了: 题意…