add convert-sorted-array-to-binary-search-tree script.

Author: everthis

108-convert-sorted-array-to-binary-search-tree.js

@@ -0,0 +1,30 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {number[]} nums
+ * @return {TreeNode}
+ */
+const sortedArrayToBST = function(nums) {
+  if (nums.length == 0) {
+    return null;
+  }
+  const head = helper(nums, 0, nums.length - 1);
+  return head;
+};
+
+function helper(num, low, high) {
+  if (low > high) {
+    // Done
+    return null;
+  }
+  let mid = Math.floor((low + high) / 2);
+  let node = new TreeNode(num[mid]);
+  node.left = helper(num, low, mid - 1);
+  node.right = helper(num, mid + 1, high);
+  return node;
+}