UVa 10305 给任务排序

 1 #include<iostream>
 2 #include<cstring>
 3 using namespace std;
 4 const int maxn = 1000;
 5 
 6 int n, m, cuv[maxn][maxn], c[maxn], topo[maxn], t;
 7 
 8 bool dfs(int u)
 9 {
10     c[u] = -1; 
11     for (int v = 1; v<=n; v++) if (cuv[u][v])
12     {
13         if (c[v]<0) return false;  //存在有向环。 
14         else if (!c[v] && !dfs(v)) return false;
15     }
16     c[u] = 1; topo[--t] = u;
17     return true;
18 }
19 
20 bool toposort()
21 {
22     t = n;
23     memset(c, 0, sizeof(c));
24     for (int u = 1; u <= n; u++) if (!c[u])
25     if (!dfs(u)) return false;
26     return true;
27 }
28 
29 int main()
30 {
31     while (cin >> n >> m && n)
32     {
33         memset(cuv, 0, sizeof(cuv));
34         for (int i = 1; i <= m; i++)
35         {
36             int u, v;
37             cin >> u >> v;
38             cuv[u][v] = 1;
39         }
40         if (toposort())
41         {
42             for (int i = 0; i < n - 1; i++)
43                 cout << topo[i] << " ";
44             cout << topo[n - 1] << endl;
45         }
46         else
47             printf("No\n");
48     }
49     return 0;
50 }