Solution for problem 2 (FTech Interview)

solution.py

"""
Author: hosjiu
Email: hosjiu1702@gmail.com
This python script is tested on Python 3.6.10 (on my local machine)
but it can still works for another python version >3.6
"""

from typing import List
from collections import namedtuple


def solve(arr: List) -> List:
    """ For much more clarification
    We use namedtuple instead of original tuple
    """
    Blob = namedtuple('NamedArray', ['value', 'index', 'result'] )

    """ Add Index and a 'placeholder' with
    pre-defined value None to each of element in the List
    """
    for idx, _ in enumerate(arr):
        t = [arr[idx], idx, None]
        arr[idx] = Blob(*t) # Unpacking?

    # Sort Array In-Place based on Value
    arr = sorted(arr, key=lambda x: x.value)

    # Compute and add Result
    for idx, x in enumerate(arr):
        # It's a very bad workaround I think
        # Just should use List instead of Tuple from the beginning
        x = list(x)
        x[2] = idx
        x = Blob(*x)
        arr[idx] = x

    # Re-sort Array again based on Index
    arr = sorted(arr, key=lambda x: x.index)

    return [x.result for x in arr]


if __name__ == '__main__':
    # Pre-defined test case for debugging
    test_case = [8, 1, 2, 3, 4]
    print(solve(test_case))