PAT 1134 Vertex Cover

1134 Vertex Cover (25分)

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 Specification:

Each input file contains one test case. For each case, the first line gives two positive integers N and M (both no more than 10​4​​), being the total numbers of vertices and the edges, respectively. Then M lines follow, each describes an edge by giving the indices (from 0 to N−1) of the two ends of the edge.

After the graph, a positive integer K (≤ 100) is given, which is the number of queries. Then K lines of queries follow, each in the format:

N​v​​ v[1] v[2]⋯v[N​v​​]

where N​v​​ is the number of vertices in the set, and v[i]'s are the indices of the vertices.

Output Specification:

For each query, print in a line Yes if the set is a vertex cover, or No if not.

Sample Input:

10 11
8 7
6 8
4 5
8 4
8 1
1 2
1 4
9 8
9 1
1 0
2 4
5
4 0 3 8 4
6 6 1 7 5 4 9
3 1 8 4
2 2 8
7 9 8 7 6 5 4 2

Sample Output:

No
Yes
Yes
No
No

 看給出的頂點是否覆蓋了所有的邊，是的話輸出Yes ，反之 No

STL是真的好用

#include <bits/stdc++.h>
#define Max 10024 
using namespace std;
vector<int> vec[Max]; //與 i 點關聯的 邊 
int vis[Max]; //邊數
int n, m, q, nv;
int u, v; 
int main(){
	cin >> n >> m;
	for(int i = 0; i < m; i++){
		cin >> u >> v;
		vec[u].push_back(i);
		vec[v].push_back(i); 
	} 
	cin >> q;
	while(q --) {
		memset(vis, 0, sizeof(vis));
		cin >> nv;
		for(int i = 0; i < nv; i++){
			cin >> u;
			for(int j = 0; j < vec[u].size(); j++){
				vis[vec[u][j]] = 1;
			}
		}
		int flag = 0;
		for(int i = 0; i < m; i++){
			if(vis[i] != 1) {
				flag = 1;
//				cout << "No" << endl;
				break;
			}
		}
		if(flag) cout << "No" << endl;
		else cout << "Yes" << endl;
	} 
	return 0;
}
//把每個頂點關聯的邊存儲起來 邊的編號 從 1 開始