1134 Vertex Cover (25分)---拓扑排序

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 Nv​​ 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

#include
using namespace std;
int degree[10005]={0};
vector<int>v[10005];

int main(){
	int N,V,a,b;
	scanf("%d%d",&N,&V);
	for(int i=0;i<V;i++){
		scanf("%d%d",&a,&b);
		v[a].push_back(b);
		degree[a]++;
		v[b].push_back(a);
		degree[b]++;
	}
	int k,num,id;
	scanf("%d",&k);
	for(int i=0;i<k;i++){
		int flag=0;
		scanf("%d",&num);
		bool visit[N]={false};
		vector<int>temp(degree,degree+N);
		for(int j=0;j<num;j++){
			scanf("%d",&id);
			visit[id]=true;
			for(int p=0;p<v[id].size();p++){
				if(!visit[v[id][p]])temp[v[id][p]]--;
			}
		}
		for(int i=0;i<N;i++){
			if(!visit[i]&&temp[i]!=0){
				flag=1;
				break;
			} 
		}
		if(flag==1)printf("No\n");
		else printf("Yes\n");
	}
	return 0;
}