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 104), 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:
Nv v[1] v[2]⋯v[Nv]
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
讲真 我看不懂题意是搜博客才看懂题目意思的
题目意思是 em...给出n个节点和m条边 对应输入
然后判断一下输入的集合是否能够覆盖每一条边 意思就是 比如1 4 8 这三个数字要覆盖那m条边的点 即每条边都至少有一个节点是{1,4,8}
代码:
#include<bits/stdc++.h>
using namespace std;
const int maxn = 1e4+10;
int dd[maxn];
map<int,vector<int> >mp;
int main()
{
int n,m,x,y;
scanf("%d%d", &n, &m);
for(int i = 1; i <= m ;i ++)
{
scanf("%d%d",&x, &y);
mp[x].push_back(i);
mp[y].push_back(i);
}
int k,num;
scanf("%d",&k);
while(k--)
{
scanf("%d",&num);
set<int>st;
for(int i = 1; i <= num;i++)
{
scanf("%d",&dd[i]);
for(int j = 0 ; j < mp[dd[i]].size();j++)
st.insert(mp[dd[i]][j]);
}
if(st.size() == m)
printf("Yes\n");
else
printf("No\n");
}
return 0;
}