Create 1361-validate-binary-tree-nodes.java

Author: sujal-goswami

java/1361-validate-binary-tree-nodes.java

@@ -0,0 +1,47 @@
+/*          BFS
+--------------------------------
+  Time Complexity: O(n)
+  Space Complexity: O(n)
+------------------------------*/  
+  
+class Solution {
+    public boolean validateBinaryTreeNodes(int n, int[] leftChild, int[] rightChild) {
+        int root = findRoot(n, leftChild, rightChild);
+        if(root == -1)
+            return false;
+
+        Set<Integer> visited = new HashSet<>();
+        Queue<Integer> q = new LinkedList<>();
+
+        q.add(root);
+        visited.add(root);
+
+        while(!q.isEmpty()){
+            int node = q.poll();
+            int[] childerns = {leftChild[node], rightChild[node]};
+          
+            for(int c: childerns){
+                if(c == -1)
+                    continue;
+                if(visited.contains(c))
+                    return false;
+                q.add(c);
+                visited.add(c);
+            }    
+        }
+        return visited.size() == n;    
+    }
+    private int findRoot(int n, int[] leftChild, int[] rightChild){
+        Set<Integer> set = new HashSet<>();
+        for(int lc: leftChild)
+            set.add(lc);
+        for(int rc: rightChild)
+            set.add(rc);
+
+        for(int i = 0; i < n; i++){
+            if(!set.contains(i))
+                return i;
+        } 
+        return -1;       
+    }
+}