Implement recursive DFS solution for LC 669 Trim a BST

Author: timothyshores

669. Trim a Binary Search Tree.js

@@ -38,4 +38,17 @@ Constraints:
  * @param {number} high
  * @return {TreeNode}
  */
-const trimBST = (root, low, high) => {};
+const trimBST = (root, low, high) => {
+  const dfs = (node) => {
+    if (!node) return null;
+
+    if (node.val < low) return dfs(node.right);
+    if (node.val > high) return dfs(node.left);
+
+    node.left = dfs(node.left);
+    node.right = dfs(node.right);
+    return node;
+  };
+
+  return dfs(root);
+};

README.md

@@ -42,6 +42,7 @@ LeetCode Profile: https://leetcode.com/timothyshores/
 |[509. Fibonacci Number](https://leetcode.com/problems/fibonacci-number/)|Easy|[JavaScript](509.%20Fibonacci%20Number.js)
 |[589. N-ary Tree Preorder Traversal](https://leetcode.com/problems/n-ary-tree-preorder-traversal/)|Easy|[JavaScript](589.%20N-ary%20Tree%20Preorder%20Traversal.js)
 |[653. Two Sum IV - Input is a BST](https://leetcode.com/problems/two-sum-iv-input-is-a-bst/)|Easy|[JavaScript](653.%20Two%20Sum%20IV%20-%20Input%20is%20a%20BST.js)
+|[669. Trim a Binary Search Tree](https://leetcode.com/problems/trim-a-binary-search-tree/)|Medium|[JavaScript](669.%20Trim%20a%20Binary%20Search%20Tree.js)
 |[701. Insert into a Binary Search Tree](https://leetcode.com/problems/insert-into-a-binary-search-tree/)|Medium|[JavaScript](701.%20Insert%20into%20a%20Binary%20Search%20Tree.js)
 |[739. Daily Temperatures](https://leetcode.com/problems/daily-temperatures/)|Medium|[JavaScript](739.%20Daily%20Temperatures.js)
 |[771. Jewels And Stones](https://leetcode.com/problems/jewels-and-stones/)|Easy|[JavaScript](771.%20Jewels%20And%20Stones.js)