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

Author: everthis

156-binary-tree-upside-down.js

@@ -0,0 +1,26 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {TreeNode}
+ */
+const upsideDownBinaryTree = function(root) {
+  let curr = root
+  let next = null
+  let temp = null
+  let prev = null
+  while (curr !== null) {
+    next = curr.left
+    curr.left = temp
+    temp = curr.right
+    curr.right = prev
+    prev = curr
+    curr = next
+  }
+  return prev
+}