题目链接 题意 对给定的一张图,求其补图的联通块个数及大小. 思路 参考 ww140142. 维护一个链表,里面存放未归入到任何一个连通块中的点,即有必要从其开始进行拓展的点. 对于每个这样的点,从它开始进行 \(bfs\),将未被拓展到的点加入队列,并从链表中删除. 注意:写法上有一点要注意, 在处理完一整个连通块之后,记录下下一个连通块中的第一个点之后,再将最初的 \(src\) 从链表中删除.若一开始便删除,则会造成链表脱节. Code #include <bits/stdc++.h>…

Description 题库链接 给你一个 \(n\) 个点 \(m\) 条边的无向图,求其补图的连通块个数及各个连通块大小. \(1\leq n,m\leq 200000\) Solution 参考了 ww140142 的做法.题解也转自该博客. 每次枚举一个未处理过的点,然后从它开始宽搜出它所在的连通块: 具体是枚举它的所有原图的边,标记起来,枚举边之后再枚举所有的点,将未标记的点加入该连通块,并加入队列继续宽搜: 为了节约无用的枚举,我们还需要对所有点构建链表,将已经在某个块内的点删除:…

补图连通块个数这大概是一个套路吧,我之前没有见到过,想了好久都没有想出来QaQ 事实上这个做法本身就是一个朴素算法,但进行巧妙的实现,就可以分析出它的上界不会超过 $O(n + m)$. 接下来介绍一下这个技巧: 很显然一个不在原图中的边一定在补图中出现,如果我们考虑用朴素的$Bfs$求一个图中的连通块个数,对于当前的一个点$x$,枚举它连出去的边进行拓展即可. 如果是求补图中的,那对于当前队首的点$x$,可以枚举其他所有的点,看是否和这个点有连边,没有就拓展. 一个可以的优化就是,一个点在$B…

E - Connected Components? 思路: 补图bfs,将未访问的点存进set里 代码: #include<bits/stdc++.h> using namespace std; #define ll long long #define pb push_back #define mem(a,b) memset(a,b,sizeof(a)) ; bool vis[N]; int head[N]; int a[N]; ,ans=; struct edge{ int to,next;…

一.题面 here 二.分析 这题刚开始没读懂题意,后来明白了,原来就是一个数连通块里点数的问题.首先在建图的时候,只考虑红色路径上的点.为什么呢,因为为了不走红色的快,那么我们可以反着想只走红色的路径,这样把所有的可能数再减去只走红色路径的数就是最终的答案了.这里要注意的是,如果连通块里只有一个点,那么就是K个点都是这个点的情况,根据题意是不满足的,也要减去. 三.AC代码 #include<bits/stdc++.h> using namespace std; typedef long l…

题意:给定一个图,问你有几个连通块. 析:不用说了,最简单的DFS. 代码如下: #include <bits/stdc++.h> using namespace std; const int maxn = 100 + 5; const int dr[] = {1, -1, 0, 0}; const int dc[] = {0, 0, 1, -1}; char a[maxn][maxn]; int vis[maxn][maxn]; void dfs(int r, int c){ vis[r][…

很有意思的一道并查集  题意:给你n个点(<=500个),m条边(<=10000),q(<=20000)个询问.对每个询问的两个值xi yi,表示在从m条边内删除[xi,yi]的边后连接剩下的边,最后求连通块的总个数 求连通块的个数很容易想到并查集,即把每两块并在一起(祖先任选),可以相连就减一.但是每次询问最多需要m次维护.而某两个点可能直接或间接相连多遍,所以删边后此边上的两个点就不一定不相连(离线莫队处理失败).但是我们可以看点数并不多,所以关键从从点入手.  模拟前缀和,并以空间…

题目链接: C. Three States time limit per test 5 seconds memory limit per test 512 megabytes input standard input output standard output The famous global economic crisis is approaching rapidly, so the states of Berman, Berance and Bertaly formed an allia…

Connected Components? CodeForces - 920E You are given an undirected graph consisting of n vertices and edges. Instead of giving you the edges that exist in the graph, we give you m unordered pairs (x, y) such that there is no edge between x and y, an…

https://codeforces.com/contest/920/problem/E https://www.luogu.org/problemnew/show/P3452 https://www.lydsy.com/JudgeOnline/problem.php?id=1098 CF貌似出了原题? 这几个都是一样的,输入输出都一样,就是读入一张图,要求补图的连通块个数以及各个连通块大小 可以这样搞:维护一个set表示所有当前没到过的点:一开始所有点加进去 取出set中任意点作为起始点并从s…

E. Connected Components? time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output You are given an undirected graph consisting of n vertices and  edges. Instead of giving you the edges that exist i…

Given n nodes labeled from 0 to n - 1 and a list of undirected edges (each edge is a pair of nodes), write a function to find the number of connected components in an undirected graph. Example 1: 0          3 |          | 1 --- 2    4 Given n = 5 and…

D. Lakes in Berland time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output The map of Berland is a rectangle of the size n × m, which consists of cells of size 1 × 1. Each cell is either land or…

C. Edgy Trees time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output You are given a tree (a connected undirected graph without cycles) of nn vertices. Each of the n−1n−1 edges of the tree is col…

Discription You are given an undirected graph consisting of n vertices and  edges. Instead of giving you the edges that exist in the graph, we give you m unordered pairs (x, y) such that there is no edge between x and y, and if some pair of vertices…

E. Connected Components? You are given an undirected graph consisting of n vertices and edges. Instead of giving you the edges that exist in the graph, we give you m unordered pairs (x, y) such that there is no edge between x and y, and if some pair…

Given n nodes labeled from 0 to n - 1 and a list of undirected edges (each edge is a pair of nodes), write a function to find the number of connected components in an undirected graph. Example 1: 0          3 |          | 1 --- 2    4 Given n = 5 and…

Given n nodes labeled from 0 to n - 1 and a list of undirected edges (each edge is a pair of nodes), write a function to find the number of connected components in an undirected graph. Example 1: 0        3 |          | 1 --- 2    4 Given n = 5 and e…

A 水题 /*Huyyt*/ #include<bits/stdc++.h> #define mem(a,b) memset(a,b,sizeof(a)) using namespace std; typedef long long ll; typedef unsigned long long ull; ][] = {{, }, {, }, {, -}, { -, }, {, }, {, -}, { -, -}, { -, }}; , gakki = + + + + 1e9; , MAXM =…

A /*Huyyt*/ #include<bits/stdc++.h> #define mem(a,b) memset(a,b,sizeof(a)) #define pb push_back using namespace std; typedef long long ll; typedef unsigned long long ull; ][] = {{, }, {, }, {, -}, { -, }, {, }, {, -}, { -, -}, { -, }}; ; + + + + 1e9…

这道题目甚长, 代码也是甚长, 但是思路却不是太难.然而有好多代码实现的细节, 确是十分的巧妙. 对代码阅读能力, 代码理解能力, 代码实现能力, 代码实现技巧, DFS方法都大有裨益, 敬请有兴趣者耐心细读.(也许由于博主太弱, 才有此等感觉). 题目: UVa 1103 In order to understand early civilizations, archaeologists often study texts written in  ancient languages. One…

We already know of the large corporation where Polycarpus works as a system administrator. The computer network there consists of n computers and m cables that connect some pairs of computers. In other words, the computer network can be represented a…

D. Connected Components 题意 现在有n个点,m条编号为1-m的无向边,给出k个询问,每个询问给出区间[l,r],让输出删除标号为l-r的边后还有几个连通块? 思路 去除编号为[l,r]的边后,只剩下了[1,l-1]&&[r+1,m]两部分. 我们维护一个前缀以及后缀并查集,询问的时候把这两部分的边合并一下,就可以求出连通块的个数. 精辟! 代码 #include<bits/stdc++.h> #include<vector> #include…

E. Connected Components? time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output You are given an undirected graph consisting of n vertices and edges. Instead of giving you the edges that exist in…

UVA 572     DFS(floodfill)  用DFS求连通块 Time Limit:1000MS     Memory Limit:65536KB     64bit IO Format:%I64d & %I64u Description Due to recent rains, water has pooled in various places in Farmer John's field, which is represented by a rectangle of N x M…

题目链接:http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemCode=3781 Time Limit: 2 Seconds      Memory Limit: 65536 KB Leo has a grid with N rows and M columns. All cells are painted with either black or white initially. Two cells A and B are calle…

G - DFS(floodfill),推荐 Time Limit:1000MS     Memory Limit:65536KB     64bit IO Format:%I64d & %I64u Submit Status Description Due to recent rains, water has pooled in various places in Farmer John's field, which is represented by a rectangle of N x M…

It is vitally important to have all the cities connected by highways in a war. If a city is occupied by the enemy, all the highways from/toward that city are closed. We must know immediately if we need to repair any other highways to keep the rest of…

题目链接 #1381 : Little Y's Tree 时间限制:24000ms 单点时限:4000ms 内存限制:512MB 描述 小Y有一棵n个节点的树,每条边都有正的边权. 小J有q个询问,每次小J会删掉这个树中的k条边,这棵树被分成k+1个连通块.小J想知道每个连通块中最远点对距离的和. 这里的询问是互相独立的,即每次都是在小Y的原树上进行操作. 输入 第一行一个整数n,接下来n-1行每行三个整数u,v,w,其中第i行表示第i条边边权为wi,连接了ui,vi两点. 接下来一行一个整数q…

题意:8个方向如果能够连成一块就算是一个连通块,求一共有几个连通块. 分析:网上的题解一般都是dfs,但是今天发现并查集也可以解决,为了方便我自己理解大神的模板,便尝试解这道题目,没想到过了... #include <cstdio> #include <iostream> #include <sstream> #include <cmath> #include <cstring> #include <cstdlib> #include…