HDU 4857 逃生 （优先队列+反向拓扑）

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<iostream>
 4 #include<algorithm>
 5 #include<queue>
 6 #include<vector>
 7 using namespace std;
 8 const int maxn = 30000+5;
 9 
10 priority_queue<int> que;
11 vector<int> vt[maxn];
12 int du[maxn],ans[maxn];
13 int main()
14 {
15     int T,n,m;
16     scanf("%d",&T);
17     while(T--)
18     {
19         scanf("%d%d",&n,&m);
20         int u,v;
21         for(int i = 1;i <= n;++i)
22         vt[i].clear();
23         memset(du,0,sizeof(du));
24         while(m--)
25         {
26             scanf("%d%d",&u,&v);
27             du[u]++;
28             vt[v].push_back(u);
29         }
30         for(int i = 1;i <= n;++i) //把出度为0的先加到优先队列中
31         if(!du[i]) que.push(i);
32         int f = n - 1;
33         while(!que.empty())
34         {
35             int s = que.top();
36             que.pop();
37             ans[f--] = s;
38             int len = vt[s].size();
39             for(int i = 0;i < len;++i)
40             {
41                 int tt = vt[s][i];
42                 du[tt]--;
43                 if(du[tt] == 0) que.push(tt);
44             }
45         }
46         for(int i = 0;i < n;++i)
47         printf(i == 0? "%d":" %d",ans[i]);
48         puts("");
49     }
50     return 0;
51 }