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 + ];

vector<int> v[MAX + ];//记录邻接表 也可以用数组模拟 vector比较方便

set<int> s;

int color[MAX + ];

void dfs(int x) {

    if(flag) return;

    s.insert(color[x]);

    vis[x] = true;

    for(int i = ;i < v[x].size();i ++) {

        if(color[v[x][i]] == color[x]) flag = ;

        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 = ;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 = ;i < n;i ++) {

            scanf("%d",&color[i]);

        }

        s.clear();

        flag = ;

        memset(vis,false,sizeof(vis));

        for(int i = ;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\n",s.size());

    }

}