Update 156-binary-tree-upside-down.js

Author: everthis

156-binary-tree-upside-down.js

@@ -24,3 +24,17 @@ const upsideDownBinaryTree = function(root) {
   }
   return prev
 }
+
+// another
+
+const upsideDownBinaryTree = function(root) {
+  if (root == null || root.left == null) {
+    return root
+  }
+  const newRoot = upsideDownBinaryTree(root.left)
+  root.left.left = root.right
+  root.left.right = root
+  root.left = null
+  root.right = null
+  return newRoot
+}