Convert Sorted Array to Binary Search Tree

LeetCode https://leetcode.cn/problems/convert-sorted-array-to-binary-search-tree/

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public TreeNode sortedArrayToBST(int[] nums) {
        
        return helper(nums, 0, nums.length - 1);
    }

    public TreeNode helper(int[] nums, int left, int right) {

        if (left > right) {
            return null;
        }

        int mid = (left + right) / 2;

        TreeNode root = new TreeNode(nums[mid]);
        root.left = helper(nums, left, mid - 1);
        root.right = helper(nums, mid + 1, right);

        return root;
    }
}

Complexity

• Time = O(n)
• Space = O(height)