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 10​4​​), 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
           

 题目大意：给定N个顶点，M条边，题目规定一条边的两个顶点不能同色 。有则输出"NO"，否则输出共有几种颜色。

代码如下：

#include <iostream>
#include <cstdio>
#include <unordered_set>
#include <cstring>
#include <algorithm>
using namespace std;
int col[10005];

struct node {

    int x,y;
}Map[10005];

int main()
{
    int N,M,K,color;
    cin>>N>>M;
    fill(col,col+N,-1);
    for (int i=0;i<M;i++)
    {
      cin>>Map[i].x>>Map[i].y;
    }
    cin>>K;
    for (int i=0;i<K;i++)
    {
      int flag=0;
      unordered_set<int> s;//用unordered_set去重，统计颜色种类。
      for (int j=0;j<N;j++)
      {
           cin>>color;
           col[j]=color;
           s.insert(color);
      }
      for(int j=0;j<M;j++)
      {
          if (col[Map[j].x]==col[Map[j].y])
           {
               flag=1;
              break; 
           }       
      }
      if (flag)  cout<<"No"<<endl;
      else  cout<<s.size()<<"-coloring"<<endl;
    }

     return 0;
}
           

其他：

fill（）函数参数：fill(first,last,val); 

// first 为容器的首迭代器，last为容器的末迭代器，val为将要替换的值。

举例：

int a[200];
fill(a, a+100, 1);
           

注意： 

fill（）中 ，它的原理是把那一块单元赋成指定的值，也就是说任何值都可以 

memset（），则是将s所指向的某一块内存中的每个字节的内容全部设置为ch指定的ASCII值，即0 、1