108. Convert Sorted Array to Binary Search Tree

1/**
2 * Definition for a binary tree node.
3 * class TreeNode {
4 *     val: number
5 *     left: TreeNode | null
6 *     right: TreeNode | null
7 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
8 *         this.val = (val===undefined ? 0 : val)
9 *         this.left = (left===undefined ? null : left)
10 *         this.right = (right===undefined ? null : right)
11 *     }
12 * }
13 */
14
15function sortedArrayToBST(nums: number[]): TreeNode | null {
16    function build(l: number, r: number): TreeNode | null {
17        if (l > r) return null;
18        const mid = Math.floor((l + r) / 2)
19        const node = new TreeNode(nums[mid]);
20        node.left = build(l, mid - 1)
21        node.right = build(mid + 1, r)
22        return node;
23    }
24
25    return build(0, nums.length - 1)
26};