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…

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…

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…

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…

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…

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…

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…