2.16 ✅ Union Find

Union Find #

  • 灵活使用并查集的思想,熟练掌握并查集的 模板,模板中有两种并查集的实现方式,一种是路径压缩 + 秩优化的版本,另外一种是计算每个集合中元素的个数 + 最大集合元素个数的版本,这两种版本都有各自使用的地方。能使用第一类并查集模板的题目有:第 128 题,第 130 题,第 547 题,第 684 题,第 721 题,第 765 题,第 778 题,第 839 题,第 924 题,第 928 题,第 947 题,第 952 题,第 959 题,第 990 题。能使用第二类并查集模板的题目有:第 803 题,第 952 题。第 803 题秩优化和统计集合个数这些地方会卡时间,如果不优化,会 TLE。
  • 并查集是一种思想,有些题需要灵活使用这种思想,而不是死套模板,如第 399 题,这一题是 stringUnionFind,利用并查集思想实现的。这里每个节点是基于字符串和 map 的,而不是单纯的用 int 节点编号实现的。
  • 有些题死套模板反而做不出来,比如第 685 题,这一题不能路径压缩和秩优化,因为题目中涉及到有向图,需要知道节点的前驱节点,如果路径压缩了,这一题就没法做了。这一题不需要路径压缩和秩优化。
  • 灵活的抽象题目给的信息,将给定的信息合理的编号,使用并查集解题,并用 map 降低时间复杂度,如第 721 题,第 959 题。
  • 关于地图,砖块,网格的题目,可以新建一个特殊节点,将四周边缘的砖块或者网格都 union() 到这个特殊节点上。第 130 题,第 803 题。
  • 能用并查集的题目,一般也可以用 DFS 和 BFS 解答,只不过时间复杂度会高一点。
No.TitleSolutionDifficultyTimeComplexitySpaceComplexityFavoriteAcceptance
0128Longest Consecutive SequenceGoMediumO(n)O(n)❤️48.5%
0130Surrounded RegionsGoMediumO(m*n)O(m*n)36.7%
0200Number of IslandsGoMediumO(m*n)O(m*n)57.0%
0399Evaluate DivisionGoMediumO(n)O(n)59.6%
0547Number of ProvincesGoMediumO(n^2)O(n)63.7%
0684Redundant ConnectionGoMediumO(n)O(n)62.2%
0685Redundant Connection IIGoHardO(n)O(n)34.1%
0695Max Area of IslandGoMedium71.8%
0721Accounts MergeGoMediumO(n)O(n)❤️56.3%
0765Couples Holding HandsGoHardO(n)O(n)❤️56.6%
0778Swim in Rising WaterGoHardO(n^2)O(n)❤️59.8%
0785Is Graph Bipartite?GoMedium53.1%
0803Bricks Falling When HitGoHardO(n^2)O(n)❤️34.4%
0839Similar String GroupsGoHardO(n^2)O(n)48.0%
0924Minimize Malware SpreadGoHardO(m*n)O(n)42.1%
0928Minimize Malware Spread IIGoHardO(m*n)O(n)❤️42.7%
0947Most Stones Removed with Same Row or ColumnGoMediumO(n)O(n)58.9%
0952Largest Component Size by Common FactorGoHardO(n)O(n)❤️40.0%
0959Regions Cut By SlashesGoMediumO(n^2)O(n^2)❤️69.1%
0990Satisfiability of Equality EquationsGoMediumO(n)O(n)50.5%
1020Number of EnclavesGoMedium65.5%
1202Smallest String With SwapsGoMedium57.7%
1254Number of Closed IslandsGoMedium64.1%
1319Number of Operations to Make Network ConnectedGoMedium62.1%
1579Remove Max Number of Edges to Keep Graph Fully TraversableGoHard53.2%
1631Path With Minimum EffortGoMedium55.7%
——————————————————————-——-—————-—————————-————-————-

⬅️上一页

下一页➡️

Calendar Apr 8, 2023
Edit Edit this page
本站总访问量:  次 您是本站第  位访问者
pFad - Phonifier reborn

Pfad - The Proxy pFad of © 2024 Garber Painting. All rights reserved.

Note: This service is not intended for secure transactions such as banking, social media, email, or purchasing. Use at your own risk. We assume no liability whatsoever for broken pages.


Alternative Proxies:

Alternative Proxy

pFad Proxy

pFad v3 Proxy

pFad v4 Proxy