AOV网络和Kahn算法拓扑排序

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 #include<cmath>
 6 #include<queue>
 7 #include<stack>
 8 #include<map>
 9 #include<set>
10 #include<sstream>
11 #include<functional>
12 using namespace std;
13 typedef long long ll;
14 const int maxn = 1000 + 10;
15 const int INF = 1e9 + 7;
16 int T, n, m, cases;
17 vector<int>Map[maxn];
18 int Count[maxn];
19 void topo()
20 {
21     stack<int>s;//存储入度数为0的顶点
22     vector<int>v;//存取拓扑排序的答案
23     for(int i = 1; i <= n; i++)//下标从1开始
24         if(Count[i] == 0)s.push(i);
25     while(!s.empty())
26     {
27         int now = s.top();
28         v.push_back(now);
29         s.pop();
30         for(int j = 0; j < Map[now].size(); j++)
31         {
32             if((--Count[Map[now][j]]) == 0)
33             {
34                 s.push(Map[now][j]);
35             }
36         }
37     }
38     if(v.size() != n)cout<<"Network has a cycle!"<<endl;
39     else
40     {
41         cout<<"Great! There is not cycle."<<endl;
42         for(int i = 0; i < v.size(); i++)cout<<v[i]<<" ";
43         cout<<endl;
44     }
45 }
46 int main()
47 {
48     while(cin >> n >> m)
49     {
50         if(!n && !m)break;
51         int u, v;
52         for(int i = 0;  i <= n; i++)Map[i].clear();
53         memset(Count, 0, sizeof(Count));
54         for(int i = 0; i < m; i++)
55         {
56             cin >> u >> v;
57             Map[u].push_back(v);
58             Count[v]++;//存入度
59         }
60         topo();
61     }
62     return 0;
63 }