Create Course_Schedule_II.java

Author: 17tanya

GraphsDFS&BFS/Course_Schedule_II.java

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+//Leetcode 210. Course Schedule II
+//Question - https://leetcode.com/problems/course-schedule-ii/
+//Kahn's Topological Sort
+
+class Solution {
+    public int[] findOrder(int numCourses, int[][] prerequisites) {
+        int result[] = new int[numCourses];
+        int cntVertex = 0;
+        Queue<Integer> inDegree0 = new LinkedList<>();
+        int inDegree[] = new int[numCourses];
+        Arrays.fill(inDegree,0);
+        
+        for(int i=0 ; i<prerequisites.length ; i++){
+            inDegree[prerequisites[i][0]]++;
+        }
+        
+        for(int i=0 ; i<numCourses ; i++){
+            if(inDegree[i]==0) inDegree0.add(i);
+        }
+        
+        while(!inDegree0.isEmpty()){
+            int curr = inDegree0.poll();
+            ArrayList<Integer> neighbours = findNeighbours(prerequisites,curr);
+            result[cntVertex] = curr;
+            
+            for(int neighbour : neighbours){
+                if(--inDegree[neighbour]==0) inDegree0.add(neighbour);
+            }
+            cntVertex++;
+        }
+        
+        if(cntVertex!=numCourses) return (new int[0]);
+        else return result;
+    }
+    
+    public ArrayList<Integer> findNeighbours(int[][] prerequisites, int v){
+        ArrayList<Integer> neighbours = new ArrayList<Integer>();
+        for(int i=0;i<prerequisites.length;i++){
+            if(prerequisites[i][1]==v) neighbours.add(prerequisites[i][0]);
+        }
+        return neighbours;
+    }
+}