LC 108. Convert Sorted Array to Binary Search Tree.java

/**
 * 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) {
        if (nums.length == 0) return null;
        return constructBST(nums, 0, nums.length - 1);
    }

    TreeNode constructBST(int[] nums, int low, int high) {
        if (low > high) return null;

        int mid = low + high >> 1;
        TreeNode cur = new TreeNode(nums[mid]);
        cur.left = constructBST(nums, low, mid - 1);
        cur.right = constructBST(nums, mid + 1, high);
        return cur;
    }
}