Leetcode (Python): Convert Sorted Array to Binary Search Tree

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

Solution:

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

class Solution:
    # @param num, a list of integers
    # @return a tree node
    def sortedArrayToBST(self, num):
        return self.sortedArrayToBSTRec(num, 0, len(num)-1)
        
    def sortedArrayToBSTRec(self, num, begin, end):
        if begin>end:
            return None
        midPoint = (begin+end)//2
        root = TreeNode(num[midPoint])
        root.left = self.sortedArrayToBSTRec(num, begin, midPoint-1)
        root.right = self.sortedArrayToBSTRec(num, midPoint+1,end)
        return root