Leetcode Problem 108 Convert Sorted Array to Binary Search Tree.txt

108. Convert Sorted Array to Binary Search Tree
Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

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.

Example:

Given the sorted array: [-10,-3,0,5,9],

One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:

      0
     / \
   -3   9
   /   /
 -10  5


Hint to solve: Calculate the mid element in the recursive call.


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

class Solution:
    
    
    def constructRecusiveBST(self, nums, start, end):
        if(start > end):
            return None
        
        mid = (int)((start+end)/2)
        #print(F"start: {start} mid:{mid} end:{end} currentElement:{nums[mid]}")

        currentNode = TreeNode(nums[mid])
        currentNode.left = self.constructRecusiveBST(nums, start, mid-1)
        currentNode.right = self.constructRecusiveBST(nums, mid+1, end)
        
        return currentNode
    
    def sortedArrayToBST(self, nums: List[int]) -> TreeNode:
        return self.constructRecusiveBST(nums, 0, len(nums)-1)