public TreeNode sortedArrayToBST(int[] nums) {
return sortedArrayToBST(nums, 0, nums.length);
}
private TreeNode sortedArrayToBST(int[] nums, int start, int end) {
if (start == end) {
return null;
}
int mid = (start + end) >>> 1;
TreeNode root = new TreeNode(nums[mid]);
root.left = sortedArrayToBST(nums, start, mid);
root.right = sortedArrayToBST(nums, mid + 1, end);
return root;
}