leetcode210

public class Solution {

    //test case [1,0]
    public int[] findOrder(int numCourses, int[][] prerequisites) {
        int[] map = new int[numCourses];
        int n = prerequisites.length;
        int[] res = new int[numCourses];

        for(int i=; i<n; i++) {
            map[ prerequisites[i][] ] ++;
        }

        Queue<Integer> que = new LinkedList<Integer>();
        int index = numCourses-;
        for(int i=; i<numCourses; i++) {
            if(map[i] == ) {
                que.add(i);
                res[index--] = i;
            }
        }

        while(!que.isEmpty() ){
            int k = que.remove();
            for(int i=; i<n; i++) {
                int l = prerequisites[i][];
                if(k==prerequisites[i][]) {
                    map[l]--;
                    if(map[l] == ) {
                        que.add(l);
                        res[index--] = l;
                    }
                }
            }
        }
        if(index!=-) return new int[];
        else return res;
    }
}

补充一个python的实现，使用深度优先遍历，进行拓扑排序：

 class Solution:
     def dfs(self,visited,memo,dic,i,postCourse):
         if visited[i]:
             return True
         if memo[i] == :
             return False
         elif memo[i] == :
             return True
         for cs in dic[i]:
             visited[i] = True
             bl = self.dfs(visited,memo,dic,cs,postCourse)
             visited[i] = False
             if bl:
                 memo[i] =
                 return True
         memo[i] =
         postCourse.append(i)
         return False
     def findOrder(self, numCourses: int, prerequisites: 'List[List[int]]') -> 'List[int]':
         dic = {}
         n = len(prerequisites)
         for i in range(numCourses):
             dic[i] = []
         for i in range(n):
             cs = prerequisites[i][]#当前课程
             pre = prerequisites[i][]#前置课程
             dic[cs].append(pre)
         visited = [False for _ in range(numCourses)]
         memo = [- for _ in range(numCourses)]
         postCourse = []
         for i in range(numCourses):
             if self.dfs(visited,memo,dic,i,postCourse):
                 return []
         return postCourse