Create Binary Tree Upside Down.js

Author: paopao2

Binary Tree Upside Down.js

@@ -0,0 +1,47 @@
+/**
+ Given a binary tree where all the right nodes are either leaf nodes with a sibling (a left node that shares the same parent node) or empty, flip it upside down and turn it into a tree where the original right nodes turned into left leaf nodes. Return the new root.
+For example:
+Given a binary tree {1,2,3,4,5},
+
+    1
+   / \
+  2   3
+ / \
+4   5
+
+return the root of the binary tree [4,5,2,#,#,3,1].
+
+   4
+  / \
+ 5   2
+    / \
+   3   1  
+
+confused what "{1,#,2,3}" means? > read more on how binary tree is serialized on OJ.
+*/
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {TreeNode}
+ */
+var upsideDownBinaryTree = function(root) {
+    if (!root || (!root.left && !root.right)) {
+        return root;
+    }
+    
+    let newRoot = upsideDownBinaryTree(root.left);
+    
+    root.left.left = root.right;
+    root.left.right = root;
+    
+    root.left = null;
+    root.right = null;
+    
+    return newRoot;
+};