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

sorted_arr_2_balan_bst.py

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#   2 3 6 8 10 12 14 20 22 28 30
class Solution(object):
    
    def to_bst(self, nums):
        if not nums:
            return
        
        mid = len(nums)/2;
        root = TreeNode(nums[mid])
        root.left = self.to_bst(nums[0:mid])
        root.right = self.to_bst(nums[mid+1:])
        
        return root
    
    def sortedArrayToBST(self, nums):
        """
        :type nums: List[int]
        :rtype: TreeNode
        """
        if not nums:
            return
        return self.to_bst(nums)