poj2492 A Bug's Life

题意：

判断一个无向图是不是二分图。

思路：

深搜。

实现：

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <vector>
 4 #include <cstring>
 5 using namespace std;
 6 
 7 const int MAXN = 2000;
 8 vector<int> G[MAXN + 5];
 9 int T, n, m, x, y, color[MAXN + 5];
10 
11 bool dfs(int x, int c)
12 {
13     color[x] = c;
14     for (int i = 0; i < G[x].size(); i++)
15     {
16         int t = G[x][i];
17         if (color[t] == c)
18             return false;
19         if (color[t] == 0 && !dfs(t, -c))
20             return false;
21     }
22     return true;
23 }
24 
25 int main()
26 {
27     cin >> T;
28     for (int t = 1; t <= T; t++)
29     {
30         cin >> n >> m;
31         for (int i = 1; i <= n; i++)
32         {
33             G[i].clear();
34         }
35         memset(color, 0, sizeof(color));
36         for (int i = 0; i < m; i++)
37         {
38             scanf("%d %d", &x, &y);
39             G[x].push_back(y);
40             G[y].push_back(x);
41         }
42         bool flag = true;
43         for (int i = 1; i <= n; i++)
44         {
45             if (!color[i])
46             {
47                 if (!dfs(i, 1))
48                 {
49                     flag = false;
50                     break;
51                 }
52             }
53         }
54         cout << "Scenario " << "#" << t << ":" << endl;
55         if (!flag)
56         {
57             cout << "Suspicious bugs found!" << endl << endl;
58          }
59         else
60         {
61             cout << "No suspicious bugs found!" << endl << endl;
62         }
63     }
64     return 0;
65 }

总结：

还可以使用并查集。