拓扑

#include <vector> class Solution { public:     /**      * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可      *      *       * @param numCows int整型       * @param feedOrders int整型vector<vector<>>       * @return int整型vector      */     vector<int> findFeedOrderII(int numCows, vector<vector<int> >& feedOrders) {         // write code here         // 每个先节点对应的后节点         vector<vector<int>> v(numCows);         // 每个节点的度         vector<int> edg(numCows);          for(const auto info:feedOrders)         {             v[info[1]].emplace_back(info[0]);             ++edg[info[0]];         }          queue<int> q;         for(int i=0; i<numCows; ++i)         {             if(edg[i]==0)                 q.emplace(i);         }          vector<int> ans;         while(!q.empty())         {             int t = q.front();             q.pop();             --numCows;             ans.emplace_back(t);              for(auto x:v[t])             {                 --edg[x];                  if(edg[x]==0)                     q.emplace(x);             }         }          if(numCows==0)             return ans;                  return vector<int>();     } };