Python Binary Search Tree: Convert a array to Binary Search Tree (BST)

Last update on July 28 2025 12:56:40 (UTC/GMT +8 hours)

5. Array to Height Balanced BST

Write a Python program to convert a given array of elements to a height balanced Binary Search Tree (BST).

Note: The selection sort improves on the bubble sort by making only one exchange for every pass through the list.

Sample Solution:

Python Code:

class TreeNode(object):
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

def array_to_bst(array_nums):
    if not array_nums:
        return None
    mid_num = len(array_nums)//2
    node = TreeNode(array_nums[mid_num])
    node.left = array_to_bst(array_nums[:mid_num])
    node.right = array_to_bst(array_nums[mid_num+1:])
    return node

def preOrder(node): 
    if not node: 
        return      
    print(node.val)
    preOrder(node.left) 
    preOrder(node.right)   

array_nums = [1,2,3,4,5,6,7]

print("Original array:")
print(array_nums)
result = array_to_bst(array_nums)
print("\nArray to a height balanced BST:")
print(preOrder(result))

Sample Output:

Original array:
[1, 2, 3, 4, 5, 6, 7]

Array to a height balanced BST:
4
2
1
3
6
5
7
None

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to convert a sorted array into a height balanced BST and then perform a pre-order traversal to display the structure.
Write a Python script to build a height balanced BST from an array and then compare the heights of its left and right subtrees for every node.
Write a Python program to create a height balanced BST from a sorted array and then calculate and print its balance factor at the root.
Write a Python function to generate a height balanced BST from a sorted list and then serialize the tree into a list using level order traversal.

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Python Code Editor:

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