A vertex cover of a graph is a set of vertices such that each edge of the graph is incident to at least one vertex of the set. Now given a graph with several vertex sets, you are supposed to tell if each of them is a vertex cover or not. Input Specif…

题目 A vertex cover of a graph is a set of vertices such that each edge of the graph is incident to at least one vertex of the set. Now given a graph with several vertex sets, you are supposed to tell if each of them is a vertex cover or not. Input Spe…

1134 Vertex Cover (考察散列查找,比较水~) 我先在CSDN上发布的该文章,排版稍好https://blog.csdn.net/weixin_44385565/article/details/88897469 Input Specification: Each input file contains one test case. For each case, the first line gives two positive integers N and M (both no…

https://pintia.cn/problem-sets/994805342720868352/problems/994805346428633088 A vertex cover of a graph is a set of vertices such that each edge of the graph is incident to at least one vertex of the set. Now given a graph with several vertex sets, y…

A vertex cover of a graph is a set of vertices such that each edge of the graph is incident to at least one vertex of the set. Now given a graph with several vertex sets, you are supposed to tell if each of them is a vertex cover or not. Input Specif…

题意:给出一个图和k个查询,每个查询给出Nv个结点,问与这些结点相关的边是否包含了整个图的所有边. 思路:首先,因为结点数较多,用邻接表存储图,并用unordered_map<int,unordered_map<int,bool>> mp;表示两个顶点的相邻关系.查询时,每读入一个结点,就删除与该结点相邻的所有邻边,若最后删除的边数恰等于图的总边数,输出Yes:否则输出No.ps.其实无需额外用vector<int> Adj[]存储图,因为unordered_map&l…

1134. Vertex Cover (25) 时间限制 600 ms 内存限制 65536 kB 代码长度限制 16000 B 判题程序 Standard 作者 CHEN, Yue A vertex cover of a graph is a set of vertices such that each edge of the graph is incident to at least one vertex of the set. Now given a graph with several…

Source: PAT A1134 Vertex Cover (25 分) Description: A vertex cover of a graph is a set of vertices such that each edge of the graph is incident to at least one vertex of the set. Now given a graph with several vertex sets, you are supposed to tell if…

A vertex cover of a graph is a set of vertices such that each edge of the graph is incident to at least one vertex of the set. Now given a graph with several vertex sets, you are supposed to tell if each of them is a vertex cover or not. Input Specif…

A vertex cover of a graph is a set of vertices such that each edge of the graph is incident to at least one vertex of the set. Now given a graph with several vertex sets, you are supposed to tell if each of them is a vertex cover or not. Input Specif…

这里将讲解一下npc问题中set cover和vertex cover分别是什么. set cover: 问题定义: 实例:现在有一个集合A,其中包含了m个元素(注意,集合是无序的,并且包含的元素也是不相同的),现在n个集合,分别为B1.B2.....Bn.并且这n个集合的并集恰好等于A集合,即:B1UB2UB3U...UBn=A. 问题:是否存在B集合的最小子集,且他们的并集也等于A集合? 例子:集合A={1,2,3,4,5},集合B={{1,2,3},{2,4},{3,4},{4,5}}.可…

2038. Minimum Vertex Cover Time limit: 1.0 secondMemory limit: 64 MB A vertex cover of a graph is a set of vertices such that each edge of the graph is incident to at least one vertex of the set. A minimum vertex cover is a vertex cover with minimal…

A vertex cover of a graph is a set of vertices such that each edge of the graph is incident to at least one vertex of the set. Now given a graph with several vertex sets, you are supposed to tell if each of them is a vertex cover or not. Input Specif…

Vertex Cover Problem's Link Mean: 给你一个无向图,让你给图中的结点染色,使得:每条边的两个顶点至少有一个顶点被染色.求最少的染色顶点数. analyse: 裸的最小点覆盖问题,二分图的最大匹配,直接套模版即可. Time complexity: O(N^2) view code…

Vertex Cover frog has a graph with \(n\) vertices \(v(1), v(2), \dots, v(n)\) and \(m\) edges \((v(a_1), v(b_1)), (v(a_2), v(b_2)), \dots, (v(a_m), v(b_m))\). She would like to color some vertices so that each edge has at least one colored vertex. Fi…

Vertex Cover frog has a graph with nn vertices v(1),v(2),…,v(n)v(1),v(2),…,v(n) and mm edges (v(a1),v(b1)),(v(a2),v(b2)),…,(v(am),v(bm))(v(a1),v(b1)),(v(a2),v(b2)),…,(v(am),v(bm)). She would like to color some vertices so that each edge has at least…

思路来自 ICPCCamp /* HDU 6150 - Vertex Cover [ 构造 ] | 2017 中国大学生程序设计竞赛 - 网络选拔赛 题意: 给了你一个贪心法找最小覆盖的算法,构造一组数据,使得这个程序跑出的答案是正解的三倍以上 分析: 构造一个二分图,左边 n 个节点 将左边的点进行 n 次分块,第 i 次分 n/i 块,每块的大小为 i,对于每一块都在右边建一个新的节点和这一块所有的点相连 则右边有 nlogn个节点,且每次一定优先选右边,最后取 nlogn >= 3n */…

传送门 Vertex Cover frog has a graph with n vertices v(1),v(2),…,v(n)v(1),v(2),…,v(n) and m edges (v(a1),v(b1)),(v(a2),v(b2)),…,(v(am),v(bm))(v(a1),v(b1)),(v(a2),v(b2)),…,(v(am),v(bm)). She would like to color some vertices so that each edge has at leas…

A vertex cover of a graph is a set of vertices such that each edge of the graph is incident to at least one vertex of the set. Now given a graph with several vertex sets, you are supposed to tell if each of them is a vertex cover or not.Input Specifi…

A proper vertex coloring is a labeling of the graph's vertices with colors such that no two vertices sharing the same edge have the same color. A coloring using at most k colors is called a (proper) k-coloring. Now you are supposed to tell if a given…

题目 A proper vertex coloring is a labeling of the graph's vertices with colors such that no two vertices sharing the same edge have the same color. A coloring using at most k colors is called a (proper) k-coloring. Now you are supposed to tell if a gi…

i 表示节点 i ,j=0表示不选择其父节点,j=1表示选择其父节点.f 为其父节点. 取 每个节点选择/不选择 两者中较小的那个. 一组数据: 151 21 31 41 1010 910 1112 1012 1410 1313 154 55 74 66 8 答案是6 #include <cstdio> #include <cstring> #include <cstdlib> #include <algorithm> #include <vector…

算是个经典题目了,很模板的树形DP题目 做这个题的时候一开始就想到树形DP了,可是由于各种原因没写出来,代码太糟烂了,赛后还是改了好久才过的 dp(u,0)=sum(dp(v,1)): dp(u,1)=sum(min(dp(v,0),dp(v,1))): #include <stdio.h> #include <string.h> #include <vector> #include <algorithm> using namespace std; vect…

题目意思: 一棵树,找到最少的点能覆盖到所有的边,(也就是每条边俩端 至少有一个在你找到的集合): 解法:每条边只能被俩个点中的一个,或全部覆盖所以我们有树形DP来解: DP[num][flag]//代表在子树NUM全部被覆盖的情况下,flag=1,这个店也被覆盖:flag=false  这个店没被覆盖: 那么有了这样的想法大妈就很好写了毕竟树形DP  主要的初始化和合并的状态: #include <cstring> #include <cstdio> #include <a…

原题传送门 求树的最小点覆盖,就是一个树形dp 类似于没有上司的舞会 dp的状态为\(f[i][0/1]\),表示i节点是否选择 边界是\(f[x][0]=0\),\(f[x][1]=1\) 转移方程是 \(f[i][0]=\sum_{j=son[i]} f[j][1]\) \(f[i][1]=\sum_{j=son[i]} Min(f[j][0],f[j][1])\) 最后答案就是\(Min(f[1][0],f[1][1])\) #include <bits/stdc++.h> #defin…

题意: 给出n个点,m条边,将若干个点染色,使得每个边至少有一点染色,问至少染多少个点. 思路: 如果是二分图,那就是最小点覆盖,但是这是一般图. 一般图的最小覆盖是npc问题,但是这题有一个条件比较特殊,就是输入的每条边都保证了至少有一个点小于等于30,所以至多覆盖30个点就可以了. 那么就可以用搜索解决,对于一个点,要么覆盖,要么不覆盖. 如果这个点被覆盖了,就直接往下搜: 如果没有被覆盖,那么就要么覆盖这个点,直接往下搜:要么不覆盖这个点,但把这个点相邻的点全部覆盖,再往下搜. 得剪枝,可…

题意:每一条边至少有一个端点要涂颜色,问最少涂几个点 思路:最小顶点覆盖:用最少的点,让每条边都至少和其中一个点关联,显然是道裸最小顶点覆盖题: 参考:二分图 代码: #include<iostream> #include<algorithm> #include<cstdio> #include<stdio.h> #include<string.h> #include<queue> #include<cmath> #inc…

http://acm.hdu.edu.cn/showproblem.php?pid=6150 #include<iostream> #include<algorithm> #include<cstring> #include<cstdio> #include<vector> #include<stack> #include<queue> #include<cmath> #include<map> #…

问题描述:就是在图中找最小的点集,使得覆盖所有边. 和独立集等价:独立集问题:在图中找最大的点集,使得点集内的所有点互不相连. 引理:顶点覆盖集和独立集互补. 上面这个引理使得这两个问题可以相互规约,从而这两个问题等价. 等价问题:给定图G和数k, 问G包含大小至少为k的独立集吗? 为什么等价:如果我们能在多项式时间内给出这个问题的答案,那么我们可以通过二分查找得到最大独立集的size为K.一个点如果是最大独立集中的点,等价于除去这个点后得到的图G'含有一个K-1大小的独立集.那么我们每次选取一…

题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=6150 题意:"最小点覆盖集"是个NP完全问题 有一个近似算法是说—每次选取度数最大的点(如果有多个这样的点,则选择最后一个) 让你构造一个图,使得其近似算法求出来点数是你给定的覆盖点数的至少3倍. 解法: 可以把左边的点编号1~n,将左边的点进行n次分块,第i次分块中每块的大小为i,对于每一块的点,都在右边创建一个新节点与这些点相连. ①右边的点的度数为n,n-1,n-2,...,n/2,…