将升序数组转化为平衡二叉树

public class Solution {    TreeNode convert(int num[], int l, int r) {        if (l >= r) return null;        int m = (l + r) / 2;        TreeNode left = convert(num, l, m);        TreeNode root = new TreeNode(num[m]);        TreeNode right = convert(num, m + 1, r);        root.left = left;        root.right = right;        return root;    }    public TreeNode sortedArrayToBST(int[] num) {        return convert(num, 0, num.length);    }}