Add solution #653

Author: JoshCrozier

README.md

@@ -87,7 +87,7 @@
 617|[Merge Two Binary Trees](./0617-merge-two-binary-trees.js)|Easy|
 628|[Maximum Product of Three Numbers](./0628-maximum-product-of-three-numbers.js)|Easy|
 648|[Replace Words](./0648-replace-words.js)|Medium|
-653|[Two Sum IV - Input is a BST](./0653-two-sum-iv---input-is-a-bst.js)|Easy|
+653|[Two Sum IV - Input is a BST](./0653-two-sum-iv-input-is-a-bst.js)|Easy|
 686|[Repeated String Match](./0686-repeated-string-match.js)|Easy|
 700|[Search in a Binary Search Tree](./0700-search-in-a-binary-search-tree.js)|Easy|
 701|[Insert into a Binary Search Tree](./0701-insert-into-a-binary-search-tree.js)|Medium|

solutions/0653-two-sum-iv-input-is-a-bst.js

@@ -0,0 +1,36 @@
+/**
+ * 653. Two Sum IV - Input is a BST
+ * https://leetcode.com/problems/two-sum-iv-input-is-a-bst/
+ * Difficulty: Easy
+ *
+ * Given the root of a Binary Search Tree and a target number k, return true
+ * if there exist two elements in the BST such that their sum is equal to the
+ * given target.
+ */
+
+/**
+ * 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
+ * @param {number} k
+ * @return {boolean}
+ */
+var findTarget = function(root, k) {
+  const set = new Set();
+  return dfs(set, root, k);
+};
+
+function dfs(set, node, k) {
+  if (!node) return false;
+  if (set.has(k - node.val)) return true;
+
+  set.add(node.val);
+
+  return dfs(set, node.left, k) || dfs(set, node.right, k);
+}