题目

法1:递归

class Solution {public TreeNode sortedArrayToBST(int[] nums) {if (nums.length == 0) {return null;} else if (nums.length  == 1) {return new TreeNode(nums[0]);}return build(nums, 0, nums.length - 1);}public TreeNode build(int[] nums, int start, int end) {if (start > end) {return null;} else if (start == end) {return new TreeNode(nums[start]);}int mid = start + (end - start) / 2;TreeNode root = new TreeNode(nums[mid]);root.left = build(nums, start, mid - 1);root.right = build(nums, mid + 1, end);return root;}
}