Time: 6 ms (56.08%) | Memory: 46.4 MB (10.49%) - LeetSync

210-course-schedule-ii/course-schedule-ii.java

@@ -0,0 +1,48 @@
+class Solution {
+    public int[] findOrder(int numCourses, int[][] prerequisites) {
+        ArrayList<ArrayList<Integer>> graph = new ArrayList<>();
+
+        for(int i = 0; i < numCourses; i++){
+            graph.add(new ArrayList<>());
+        }
+
+        for(int i = 0; i < prerequisites.length; i++){
+            graph.get(prerequisites[i][1]).add(prerequisites[i][0]);
+        }
+
+        int[] indegree = new int[numCourses];
+        for(int i = 0; i < numCourses; i++){
+            for(int neigh: graph.get(i)){
+                indegree[neigh] ++;
+            }
+        }
+
+        Queue<Integer> q = new LinkedList<>();
+
+        for(int i = 0; i < numCourses; i++){
+            if(indegree[i] == 0){
+                q.add(i);
+            }
+        }
+        int[] topo = new int[numCourses];
+        int i = 0;
+
+        while(!q.isEmpty()){
+            int top = q.poll();
+            topo[i++] = top;    
+
+            for(int neigh: graph.get(top)){
+                indegree[neigh] --;
+                if(indegree[neigh] == 0){
+                    q.add(neigh);
+                }
+            }
+        }
+
+        if(i == numCourses){
+            return topo;
+        }else{
+            return new int[]{};
+        }
+    }
+}