1 """
2 Given an array where elements are sorted in ascending order, convert it to a height balanced BST.
3 For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
4 Example:
5 Given the sorted array: [-10,-3,0,5,9],
6 One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:
7 0
8 / \
9 -3 9
10 / /
11 -10 5
12 """
13 """
14 对于二叉搜索树，左右结点的值有规律，应该想到递归
15 二分+递归解法
16 """
17 class TreeNode:
18 def __init__(self, x):
19 self.val = x
20 self.left = None
21 self.right = None
22
23 class Solution:
24 def sortedArrayToBST(self, nums):
25 return self.convert(nums, 0, len(nums) - 1)
26
27 def convert(self, nums, left, right):
28 if left > right: # bug 没写这个判断maximum recursion depth exceeded
29 return None
30 mid = (left + right) // 2
31 Node = TreeNode(nums[mid])
32 Node.left = self.convert(nums, left, mid - 1)
33 Node.right = self.convert(nums, mid + 1, right)
34 return Node
