Python Binary Search Tree: Find the closest value of a target in a given non-empty Binary Search Tree (BST) of unique values

Last update on May 28 2022 13:30:46 (UTC/GMT +8 hours)

Python Binary Search Tree: Exercise-2 with Solution

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.

Sample Solution:

Python Code:

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

def closest_value(root, target):
    a = root.val
    kid = root.left if target < a else root.right
    if not kid:
        return a
    b = closest_value(kid, target)
    return min((a,b), key=lambda x: abs(target-x))

root = TreeNode(8)  
root.left = TreeNode(5)  
root.right = TreeNode(14) 
root.left.left = TreeNode(4)  
root.left.right = TreeNode(6) 
root.left.right.left = TreeNode(8)  
root.left.right.right = TreeNode(7)  
root.right.right = TreeNode(24) 
root.right.right.left = TreeNode(22)  
    
result = closest_value(root, 19)
print(result)

Sample Output:

Flowchart:

Python Code Editor:

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Previous: 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.
Next: Write a Python program to check whether a given a binary tree is a valid binary search tree (BST) or not.

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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