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Python Binary Search Tree: Create a Balanced Binary Search Tree (BST) using an sorted array

Python Binary Search Tree: Exercise-1 with Solution

Write a Python program to create a Balanced Binary Search Tree (BST) using an array (given) elements where array elements are sorted in ascending order.

Pictorial Presentation:

Flowchart: Create a Balanced Binary Search Tree using an sorted array

Sample Solution:

Python Code:

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

def sorted_array_to_bst(nums):
    
    if not nums:
        return None
    mid_val = len(nums)//2
    node = TreeNode(nums[mid_val])
    node.left = sorted_array_to_bst(nums[:mid_val])
    node.right = sorted_array_to_bst(nums[mid_val+1:])
    return node

def preOrder(node): 
    if not node: 
        return      
    print(node.val)
    preOrder(node.left) 
    preOrder(node.right)   
    
result = sorted_array_to_bst([1, 2, 3, 4, 5, 6, 7])
preOrder(result)

Sample Output:

4
2
1
3
6
5
7

Flowchart:

Flowchart: Create a Balanced Binary Search Tree using an sorted array

Python Code Editor:

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Next: Write a Python program to find the closest value of a given target value in a given non-empty Binary Search Tree (BST) of unique values.

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Python: Tips of the Day

Find current directory and file's directory:

To get the full path to the directory a Python file is contained in, write this in that file:

import os 
dir_path = os.path.dirname(os.path.realpath(__file__))

(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)

To get the current working directory use

import os
cwd = os.getcwd()

Documentation references for the modules, constants and functions used above:

  • The os and os.path modules.
  • The __file__ constant
  • os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
  • os.path.dirname(path) (returns "the directory name of pathname path")
  • os.getcwd() (returns "a string representing the current working directory")
  • os.chdir(path) ("change the current working directory to path")

Ref: https://bit.ly/3fy0R6m