<ACM/ICPC算法训练教程>读书笔记-这一次补上并查集的部分.将对并查集的思想进行详细阐述,并附上本人AC掉POJ1703的Code. 在一些有N个元素的集合应用问题中,通常会将每个元素构成单元素集合,然后按照一定顺序将同属一组的集合合并,期间要反复查找每一个元素在哪个集合中.这类问题往往看似简单,但是数据量很大,因此容易造成TLE或MLE,也就是空间度和时间度极其复杂.因此在这里,我们引入一种抽象的特殊数据结构——并查集. 并查集:类似一个族谱,每个结点均有一个father[x]来表示x…

以下是并查集思路详解: 一:概念 并查集处理的是“集合"之间的关系.当给出两个元素的一个无序数对(a,b)时,需要快速“合并”a和b分别所在的集合,这期间需要反复“查找”某元素所在的集合.“并”,“查”,“集”三个字由此而来. 并查集是一种树型的数据结构,用于处理一些不相交集合(Disjoint Sets)的合并及查询问题. 常常在使用中以森林来表示. 集就是让每个元素构成一个单元素的集合,也就是按一定顺序将属于同一组的元素所在的集合合并. 在一些有N个元素的集合应用问题中,通常是在开始时让每个…

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Is It A Tree? Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 16702    Accepted Submission(s): 3761 Problem Description A tree is a well-known data structure that is either empty (null, void, n…

Is It A Tree? Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 26002   Accepted: 8879 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 edge…

Petya loves lucky numbers. We all know that lucky numbers are the positive integers whose decimal representations contain only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not. One day Petya encountered a tre…

tree 把每条边权是1的边断开,发现每个点离他最近的点个数就是他所在的连通块大小. 开一个并查集,每次读到边权是0的边就合并.最后Ans​i​​=size[findset(i)],size表示每个并查集根的size Ans_i=size[findset(i)],sizeAns​i​​=size[findset(i)],size表示每个并查集根的sizesize. #include<cstdio> #include<cstring> #include<algorithm>…

题目链接:http://acm.swust.edu.cn/problem/856/ Time limit(ms): 1000 Memory limit(kb): 10000 Description There are N trees in a forest. At first, each tree contains only one node as its root. And each node is marked with a number. You're asked to do the fo…

D. Fix a Tree time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output A tree is an undirected connected graph without cycles. Let's consider a rooted undirected tree with n vertices, numbered 1 th…

Is It A Tree? Time Limit:1000MS     Memory Limit:10000KB     64bit IO Format:%I64d & %I64u Submit Status 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 direct…