## DEV Community

Abhishek Chaudhary

Posted on

# Convert Sorted Array to Binary Search Tree

Given an integer array `nums` where the elements are sorted in ascending order, convert it to a height-balanced binary search tree.

A height-balanced binary tree is a binary tree in which the depth of the two subtrees of every node never differs by more than one.

Example 1:

Input: nums = [-10,-3,0,5,9]
Output: [0,-3,9,-10,null,5]
Explanation: [0,-10,5,null,-3,null,9] is also accepted:

Example 2:

Input: nums = [1,3]
Output: [3,1]
Explanation: [1,null,3] and [3,1] are both height-balanced BSTs.

Constraints:

• `1 <= nums.length <= 104`
• `-104 <= nums[i] <= 104`
• `nums` is sorted in a strictly increasing order.

SOLUTION:

``````# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
def sortedArrayToBST(self, nums: List[int]) -> Optional[TreeNode]:
n = len(nums)
if n > 1:
root = TreeNode(nums[n // 2])
root.left = self.sortedArrayToBST(nums[:n//2])
root.right = self.sortedArrayToBST(nums[1 + (n//2) :])
return root
elif n == 1:
return TreeNode(val = nums[0])
else:
return None
``````