Add solution #96

Author: JoshCrozier

README.md

@@ -79,6 +79,7 @@
 93|[Restore IP Addresses](./0093-restore-ip-addresses.js)|Medium|
 94|[Binary Tree Inorder Traversal](./0094-binary-tree-inorder-traversal.js)|Easy|
 95|[Unique Binary Search Trees II](./0095-unique-binary-search-trees-ii.js)|Medium|
+96|[Unique Binary Search Trees](./0096-unique-binary-search-trees.js)|Medium|
 98|[Validate Binary Search Tree](./0098-validate-binary-search-tree.js)|Medium|
 100|[Same Tree](./0100-same-tree.js)|Easy|
 101|[Symmetric Tree](./0101-symmetric-tree.js)|Easy|

solutions/0096-unique-binary-search-trees.js

@@ -0,0 +1,20 @@
+/**
+ * 96. Unique Binary Search Trees
+ * https://leetcode.com/problems/unique-binary-search-trees/
+ * Difficulty: Medium
+ *
+ * Given an integer n, return the number of structurally unique BST's (binary
+ * search trees) which has exactly n nodes of unique values from 1 to n.
+ */
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var numTrees = function(n) {
+  return traverse(2 * n) / (traverse(n + 1) * traverse(n));
+};
+
+function traverse(n) {
+  return n <= 0 ? 1 : n * traverse(n - 1);
+}