Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

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

2/17/2017, Java

performance不好

1 public class Solution { 2     public TreeNode sortedArrayToBST(int[] nums) { 3         if (nums == null) return null; 4         return sortedArrayToBST(nums, 0, nums.length - 1); 5     } 6     private TreeNode sortedArrayToBST(int[] nums, int lo, int hi) { 7         if (lo > hi) return null; 8         int mid = lo + (hi - lo) / 2; 9         TreeNode ret = new TreeNode(nums[mid]);10         ret.left = sortedArrayToBST(nums, lo, mid - 1);11         ret.right = sortedArrayToBST(nums, mid + 1, hi);12         return ret;13     }14 }