Add solution #222

Author: JoshCrozier

README.md

@@ -196,6 +196,7 @@
 217|[Contains Duplicate](./0217-contains-duplicate.js)|Easy|
 219|[Contains Duplicate II](./0219-contains-duplicate-ii.js)|Easy|
 220|[Contains Duplicate III](./0220-contains-duplicate-iii.js)|Hard|
+222|[Count Complete Tree Nodes](./0222-count-complete-tree-nodes.js)|Easy|
 225|[Implement Stack using Queues](./0225-implement-stack-using-queues.js)|Easy|
 226|[Invert Binary Tree](./0226-invert-binary-tree.js)|Easy|
 228|[Summary Ranges](./0228-summary-ranges.js)|Easy|

solutions/0222-count-complete-tree-nodes.js

@@ -0,0 +1,29 @@
+/**
+ * 222. Count Complete Tree Nodes
+ * https://leetcode.com/problems/count-complete-tree-nodes/
+ * Difficulty: Easy
+ *
+ * Given the root of a complete binary tree, return the number of the nodes in the tree.
+ *
+ * According to Wikipedia, every level, except possibly the last, is completely filled
+ * in a complete binary tree, and all nodes in the last level are as far left as possible.
+ * It can have between 1 and 2h nodes inclusive at the last level h.
+ *
+ * Design an algorithm that runs in less than O(n) time complexity.
+ */
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number}
+ */
+var countNodes = function(root) {
+  return !root ? 0 : 1 + countNodes(root.left) + countNodes(root.right);
+};