hdu_5695_Gym Class(拓扑排序)

题目连接：http://acm.hdu.edu.cn/showproblem.php?pid=5695

题意：中文题，不解释

题解：逆向拓扑字典序就行

 #include<cstdio>
 #include<string>
 #include<set>
 #include<vector>
 #include<queue>
 #include<functional>
 using namespace std;
 #define MAX 100010
 int InDeg[MAX];
 int n, m, Count;
 int Ans[MAX];
 vector<int> v[MAX];
 void TopoSort()
 {
     priority_queue<int> PQ;
     for(int i=n; i>=; i--) //找出入度为0的点并放入优先队列
         if(InDeg[i]==) PQ.push(i);

     while(!PQ.empty()) //BFS
     {
         int Tmp = PQ.top();
         PQ.pop();
         Ans[Count++] = Tmp;
         for(int i=; i<v[Tmp].size(); i++)
         {
             InDeg[v[Tmp][i]]--;
             if(InDeg[v[Tmp][i]]==) PQ.push(v[Tmp][i]);
         }
     }
 }

 int main()
 {
     int x, y,t;
     scanf("%d",&t);
     while(t--)
     {
         scanf("%d%d",&n,&m);

         for(int i=;i<=n;i++)v[i].clear(),InDeg[i]=;
         Count = ;
         for(int i=; i<m; i++)
         {
             scanf("%d%d",&x,&y);
             InDeg[y]++;
             v[x].push_back(y);
         }
         TopoSort();
         int min=;
         long long an=;
         for(int i=; i<Count; i++){
             min=min>Ans[i]?Ans[i]:min;
             an+=min;
         }
         printf("%I64d\n",an);
     }
 }