pat甲级 1154 Vertex Coloring （25 分）

A proper vertex coloring is a labeling of the graph's vertices with colors such that no two vertices sharing the same edge have the same color. A coloring using at most kcolors is called a (proper) k-coloring.

Now you are supposed to tell if a given coloring is a proper k-coloring.

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 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 colorings you are supposed to check. Then K lines follow, each contains N colors which are represented by non-negative integers in the range of int. The i-th color is the color of the i-th vertex.

Output Specification:

For each coloring, print in a line k-coloring if it is a proper k-coloring for some positive k, 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
4
0 1 0 1 4 1 0 1 3 0
0 1 0 1 4 1 0 1 0 0
8 1 0 1 4 1 0 5 3 0
1 2 3 4 5 6 7 8 8 9

Sample Output:

4-coloring
No
6-coloring
No

遍历加判断。set记录总共包含几种颜色，如果两个相邻点颜色相同就把flag置为1。
代码：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <vector>
#include <set>
#include <algorithm>
#define MAX 10000
#define DMAX 10000
using namespace std;
typedef long long ll;
int n,m,k,flag;
bool vis[MAX + 1];
vector<int> v[MAX + 1];//记录邻接表 也可以用数组模拟 vector比较方便
set<int> s;
int color[MAX + 1];
void dfs(int x) {
    if(flag) return;
    s.insert(color[x]);
    vis[x] = true;
    for(int i = 0;i < v[x].size();i ++) {
        if(color[v[x][i]] == color[x]) flag = 1;
        if(flag) return;
        if(!vis[v[x][i]]) dfs(v[x][i]);
    }
}

int main() {
    int a,b;
    scanf("%d%d",&n,&m);
    for(int i = 0;i < m;i ++) {
        scanf("%d%d",&a,&b);
        v[a].push_back(b);
        v[b].push_back(a);
    }
    scanf("%d",&k);
    while(k --) {
        for(int i = 0;i < n;i ++) {
            scanf("%d",&color[i]);
        }
        s.clear();
        flag = 0;
        memset(vis,false,sizeof(vis));
        for(int i = 0;i < n;i ++) {///图不一定是连通图
            if(!vis[i]) {
                dfs(i);
            }
        }
        if(flag || s.empty()) puts("No");
        else printf("%d-coloring
",s.size());
    }
}