1134. Vertex Cover (25)

时间限制

600 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

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:

10 118 76 84 58 48 11 21 49 89 11 02 454 0 3 8 46 6 1 7 5 4 93 1 8 42 2 87 9 8 7 6 5 4 2

Sample Output:

NoYesYesNoNo

解题思路：

y条边以下标0~y-1的顺序依次输入，用二维数组（列长为2）将每条边的两个端点编号进行记录。

每次flag初始为1，vis数组元素全部指向0,。输入一组端点编号，将与编号相对的vis数组下标元素设为1。

接着，把y条边（0-y-1）依次遍历。若有一条边的两个端点编号均不属于输入的端点编号，则表明没有完全覆盖。此时，用flag=0做标记，跳出循环。

flag=1，输出Yes，否则，输出No。

我的代码：

#include<stdio.h>#include<memory.h>int main(){int x,y,z,i,n,m,a[10001][2],vis[10001];scanf("%d%d",&x,&y);for(i=0;i<y;i++) scanf("%d%d",&a[i][0],&a[i][1]);scanf("%d",&z);while(z--){scanf("%d",&n);memset(vis,0,sizeof(vis));int flag=1;while(n--){scanf("%d",&m);vis[m]=1;}for(i=0;i<y;i++){if(vis[a[i][0]]==0 && vis[a[i][1]]==0){flag=0;break;}}if(flag==0) puts("No");else puts("Yes");}return 0;}

提交结果：