level order travel

Author: nch3ng

Binary Tree Level Order Traversal II/Solution.rb

@@ -0,0 +1,30 @@
+# Definition for a binary tree node.
+# class TreeNode
+#     attr_accessor :val, :left, :right
+#     def initialize(val)
+#         @val = val
+#         @left, @right = nil, nil
+#     end
+# end
+
+# @param {TreeNode} root
+# @return {Integer[][]}
+def level_order_bottom(root)
+    result=[]
+    return result if root.nil?
+    q=[]
+    q.push root
+    
+    until q.empty?
+        size = q.length
+        internal_s=[]
+        1.upto(size) do |i|
+            r = q.shift
+            internal_s.push r.val
+            q.push r.left unless r.left.nil?
+            q.push r.right unless r.right.nil?
+        end
+        result.unshift internal_s
+    end
+    result
+end

README.md

@@ -23,5 +23,6 @@ Median of Two Sorted Arrays
 [Flatten Binary Tree to Linked List](https://leetcode.com/problems/flatten-binary-tree-to-linked-list/)  
 [Minimum Depth of Binary Tree](https://leetcode.com/problems/minimum-depth-of-binary-tree/)  
 [Balanced Binary Tree](https://leetcode.com/problems/balanced-binary-tree/)  
+[Binary Tree Level Order Traversal II](https://leetcode.com/problems/binary-tree-level-order-traversal-ii/)    
 
 - Until 12/5

btree_helper.rb

@@ -6,6 +6,7 @@
 [1,2,3,null,null,4]
 [3,5,1,6,2,0,8,null,null,7,4]
 [37,-34,-48,null,100,-100,48,null,null,null,null,-54,null,-71,-22,null,null,null,8]
+[3,9,20,null,null,15,7]
 =end
 
 $btree_testcase = [