面试题 04.02. 最小高度树

给定一个有序整数数组，元素各不相同且按升序排列，编写一个算法，创建一棵高度最小的二叉搜索树。

示例:
给定有序数组: [-10,-3,0,5,9],

一个可能的答案是：[0,-3,9,-10,null,5]，它可以表示下面这个高度平衡二叉搜索树：

0
/ \
-3 9
/ /
-10 5

来源：力扣（LeetCode）

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def sortedArrayToBST(self, nums: List[int]) -> TreeNode:
        def dfs(nums,l,r):
            if l==r:return 
            mid=l+(r-l)//2
            node=TreeNode(nums[mid])
            node.left=dfs(nums,l,mid)
            node.right=dfs(nums,mid+1,r)
            return node
        return dfs(nums,0,len(nums))

 

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def sortedArrayToBST(self, nums: List[int]) -> TreeNode:
        if not nums:return 
        mid=len(nums)>>1
        node=TreeNode(nums[mid])
        node.left=self.sortedArrayToBST(nums[:mid])
        node.right=self.sortedArrayToBST(nums[mid+1:])
        return node