210. Course Schedule II

 1     public int[] findOrder(int numCourses, int[][] prerequisites) {
 2         int[] result = new int[numCourses];
 3         if(numCourses < 1) {
 4             return new int[0];
 5         }
 6         int index = numCourses - 1;
 7         Queue<Integer> queue = new LinkedList<Integer>();
 8         int[] indegree = new int[numCourses];
 9         int len = prerequisites.length;
10         for(int i = 0; i < len; i++) {
11             indegree[prerequisites[i][1]]++;
12         }
13         for(int i = 0; i < numCourses; i++) {
14             if(indegree[i] == 0) {
15                 queue.offer(i);
16             } 
17         }
18         while(!queue.isEmpty()) {
19             int cur = queue.poll();
20             result[index] = cur;
21             index--;
22             for(int i = 0; i < len; i++) {
23                 if(prerequisites[i][0] == cur) {
24                     indegree[prerequisites[i][1]]--;
25                     if(indegree[prerequisites[i][1]] == 0) {
26                         queue.add(prerequisites[i][1]);
27                     }
28                 }
29             }
30         }
31         for(int i = 0; i < numCourses; i++) {
32             if(indegree[i] != 0) {
33                 return new int[0];
34             }
35         }
36         return result;
37     }