Done with BFS-1

Problem2.java

@@ -0,0 +1,43 @@
+class Solution {
+    public boolean canFinish(int numCourses, int[][] prerequisites) {
+        HashMap<Integer, List<Integer>> map= new HashMap<>();
+        int [] indegrees = new int [numCourses];
+        for(int [] edge: prerequisites){
+            int de = edge[0];
+            int inde = edge[1];
+            if(!map.containsKey(inde)){
+                map.put(inde, new ArrayList<>());
+            }
+            map.get(inde).add(de);
+            indegrees[de]++;
+        }
+        Queue <Integer> q= new LinkedList<>();
+        int count=0;
+        for(int i=0; i<numCourses;i++){
+            if(indegrees[i]==0){
+                q.add(i);
+                count++;
+            }
+        }
+        if(count==numCourses) return true;
+        if(q.isEmpty()){
+            return false;
+        }
+        while(!q.isEmpty()){
+            int curr = q.poll();
+            List<Integer> children= map.get(curr);
+            if(children != null){
+                for(int child: children){
+                indegrees[child]--;
+                if(indegrees[child]==0){
+                    q.add(child);
+                    count++;
+                    if(count==numCourses) return true;
+                }
+            }
+            }
+
+        }
+        return false;
+    }
+}