PAT甲级——A1154 VertexColoring【25】

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 k colors 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 Klines 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

Solution:
　　这道题很水，就是一个简单的判断图的边的两个顶点是不是同一个颜色，把图的精髓都没考出来，唯一有点考点的就是需要使用一个set来统计有几种颜色。

 #include <iostream>
 #include <vector>
 #include <unordered_set>
 using namespace std;
 int main()
 {
     int n, m, k;
     cin >> n >> m;
     vector <vector<int>>path(n);
     while (m--)
     {
         int a, b;
         cin >> a >> b;
         path[a].push_back(b);
         path[b].push_back(a);
     }
     cin >> k;
     while (k--)
     {
         vector<int>color(n, );
         unordered_set<int>nums;
         for (int i = ; i < n; ++i)
         {
             cin >> color[i];
             nums.insert(color[i]);
         }
         bool flag = true;
         for (int i = ; i < n && flag; ++i)
         {
             for (auto j : path[i])
             {
                 if (color[i] == color[j])
                 {
                     flag = false;
                     break;
                 }
             }
         }
         if (flag)
             printf("%d-coloring\n", nums.size());
         else
             printf("No\n");
     }
     return ;
 }