拓扑排序

• 拓扑排序

  以入度为0的做起点
  vector top_sort(){
  priority_queue ,greater >Q;
  for(int i=1;i<=n;i++){
      if(!indeg[i]){
          Q.push(i);
      }
  }
  std::vector TOP;
  while(!Q.empty()){
      int T=Q.top();
      Q.pop();
      indeg[T]=-1;
      TOP.push_back(T);
      for(auto &e:graph[T]){
          indeg[e]--;
          if(indeg[e]==0)Q.push(e);
      }
  }return TOP;
  }
  }