课程表

课程表

class Solution {
public:
 bool canFinish(int numCourses, vector<vector<int>>& prerequisites)
 {
  vector<int> indegree(numCourses);
  vector<vector<int>> graph(numCourses);
  vector<int> v;
  for (int i = 0; i<numCourses; i++)
  {
   indegree[i] = 0;
   graph.push_back(v);
  }
  for (int i = 0; i<prerequisites.size(); i++)
  {
   indegree[prerequisites[i][0]]++;
   graph[prerequisites[i][1]].push_back(prerequisites[i][0]);
  }
  queue<int> myqueue;
  for (int i = 0; i<numCourses; i++)
  {
   if (indegree[i] == 0)
   {
    myqueue.push(i);
   }
  }
  int k = 0;
  while (!myqueue.empty())
  {
   int t = myqueue.front();
   myqueue.pop();
   ++k;
   for (int i = 0; i<graph[t].size(); i++)
   {
    indegree[graph[t][i]]--;
    if (indegree[graph[t][i]] == 0)
    {
     myqueue.push(graph[t][i]);
    }
   }
  }
  return k == numCourses;
 }
};