PAT甲级——A1134 Vertex Cover【25】

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 1), 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​​ [ [

where N​v​​ is the number of vertices in the set, and ['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

mmp,看了半天都没有看懂题，英语弱到爆
百度后才知道，每条边至少有一个顶点存在set总，则该set是vertex cover

 1 #include <iostream>
 2 #include <vector>
 3 using namespace std;
 4 int a, b, n, m, k,nv;
 5 int main()
 6 {
 7     cin >> n >> m;
 8     vector<pair<int, int>>graph(m);
 9     for (int i = 0; i < m; ++i)
10         cin >> graph[i].first >> graph[i].second;
11     cin >> k;
12     while (k--)
13     {
14         cin >> nv;
15         vector<bool>map(n, false);
16         while (nv--)
17         {
18             cin >> a;
19             map[a] = true;
20         }
21         bool flag = true;
22         for (int i = 0; flag&&i < m; ++i)
23             if (map[graph[i].first] == false && map[graph[i].second] == false)//没有一个顶点存在map中
24                 flag = false;
25         cout << (flag ? "Yes" : "No") << endl;
26     }
27     return 0;
28 }