POJ 2553 The Bottom of a Graph 题目链接 题意:给定一个有向图,求出度为0的强连通分量 思路:缩点搞就可以 代码: #include <cstdio> #include <cstring> #include <algorithm> #include <vector> #include <stack> using namespace std; const int N = 5005; int n, m; vector&l…

The Bottom of a Graph Time Limit: 3000MS   Memory Limit: 65536K Total Submissions: 9641   Accepted: 4008 Description We will use the following (standard) definitions from graph theory. Let V be a nonempty and finite set, its elements being called ver…

题目是问,一个有向图有多少个点v满足∀w∈V:(v→w)⇒(w→v). 把图的强连通分量缩点,那么答案显然就是所有出度为0的点. 用Tarjan找强连通分量: #include<cstdio> #include<cstring> #include<algorithm> using namespace std; #define MAXN 5555 #define MAXM 5555*5555 struct Edge{ int u,v,next; }edge[MAXM];…

题意: 求出度为0的强连通分量. 思路: 缩点 具体有两种实现: 1.遍历所有边, 边的两端点不在同一强连通分量的话, 将出发点所在强连通分量出度+1. #include <cstdio> #include <cstring> #include <stack> #include <algorithm> using namespace std; //0.03s 4856K const int MAXN = 5005; struct Pool { int pre…

题意:给出一个有向图G,寻找所有的sink点.“sink”的定义为:{v∈V|∀w∈V:(v→w)⇒(w→v)},对于一个点v,所有能到达的所有节点w,都能够回到v,这样的点v称为sink. 分析:由(v→w),(w→v)可知,节点v,w构成强连通,很自然的想到要缩点.缩点之后,DAG上的每一条边,都是单向的(v->w),无回路(w->v). 错误:对于v可达的点w,不仅是直接连边——从一个强连通子集A到另一个强连通子集B,意味着,子集A中的点都不可能是sink点. #include<c…

题意: 求出图中所有汇点 定义:点v是汇点须满足 --- 对图中任意点u,若v可以到达u则必有u到v的路径:若v不可以到达u,则u到v的路径可有可无. 模板:http://www.cnblogs.com/Jadon97/p/8328750.html 分析: 很显然, 图中强连通分量中所有的点属性都是一样的, 要么都是汇点, 要么都不是. 如果有一个强连通分量A的边连向强连通分量B, 那么A一定不是汇点, 因为B不会有边连向A(如果有的话A.B就是同一个强连通分量了). 求出所有强连通分量, 然后…

链接: https://vjudge.net/problem/POJ-2553 题意: We will use the following (standard) definitions from graph theory. Let V be a nonempty and finite set, its elements being called vertices (or nodes). Let E be a subset of the Cartesian product V×V, its ele…

题目地址:http://poj.org/problem?id=2553 The Bottom of a Graph Time Limit: 3000MS   Memory Limit: 65536K Total Submissions: 7881   Accepted: 3263 Description We will use the following (standard) definitions from graph theory. Let V be a nonempty and finit…

The Bottom of a Graph Time Limit: 3000MS   Memory Limit: 65536K Total Submissions: 10114   Accepted: 4184 Description We will use the following (standard) definitions from graph theory. Let V be a nonempty and finite set, its elements being called ve…

The Bottom of a Graph Time Limit: 3000MS   Memory Limit: 65536K Total Submissions: 9139   Accepted: 3794 Description We will use the following (standard) definitions from graph theory. Let V be a nonempty and finite set, its elements being called ver…