topsort with DFS

Author: Arjiit

findOrder.java

@@ -0,0 +1,36 @@
+class Solution {
+/*
+Same as course schedule, as an when we are done exploring for a node i.e when we insert the element in queue, when
+we pop out, we add it to the result array.
+*/
+    public int[] findOrder(int numCourses, int[][] prerequisites) {
+        int[] inDegree = new int[numCourses];
+        int[] res = new int[numCourses];
+        for (int i=0; i< prerequisites.length;i++) {
+            inDegree[prerequisites[i][0]]++;
+        }
+        
+        Queue<Integer> q = new LinkedList<>();
+        for (int j=0; j<inDegree.length; j++) {
+            if (inDegree[j] == 0) {
+                q.offer(j);
+            }
+        }
+        int k = 0;
+        while(!q.isEmpty()) {
+            int out = q.poll();
+            res[k] = out;
+            k++;
+            for (int i=0; i<prerequisites.length; i++) {
+                if (prerequisites[i][1] == out) {
+                    inDegree[prerequisites[i][0]]--;
+                    if (inDegree[prerequisites[i][0]] == 0) {
+                        q.offer(prerequisites[i][0]);
+                    }
+                }
+            }
+            
+        }
+        return numCourses == k ? res: new int[]{};   
+    }
+}