Solution for problem 5 (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


def solve(arr: List) -> List:
    # Join strings
    end_string = ''
    for string in arr:
        end_string += string

    s = set()
    count_dict = {}
    for c in end_string:
        # If the char was not inside the set before
        if not c in s:
            s.add(c)
            count_dict[c] = 1
        # Otherwise we update number of its occurrences
        else:
            count_dict[c] += 1

    ret = [k for k, v in count_dict.items() if v >= 3]
    return ret


if __name__ == '__main__':
    test_case_ex = ['bella', 'hosjiu', 'something', 'went', 'wrong']
    print(solve(test_case_ex))