Binary Tree Level Order Traversal II

Author: parshva45

Binary Tree Level Order Traversal II.js

@@ -0,0 +1,48 @@
+/*Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).
+
+For example:
+Given binary tree [3,9,20,null,null,15,7],
+    3
+   / \
+  9  20
+    /  \
+   15   7
+return its bottom-up level order traversal as:
+[
+  [15,7],
+  [9,20],
+  [3]
+]*/
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number[][]}
+ */
+var levelOrderBottom = function(root) {
+    ans = []
+    h = 0
+    lobHelper(root,ans,h)
+    return ans.reverse()
+};
+
+var lobHelper = function(node,ans,h){
+    if(node != null){
+        if(ans.length == h){
+            ans[h] = []
+        }
+        ans[h].push(node.val)
+        if(node.left != null){
+            lobHelper(node.left,ans,h+1)
+        }
+        if(node.right != null){
+            lobHelper(node.right,ans,h+1)
+        }
+    }
+};