multitap.py

import itertools


def decode_multi_tap(multitap_encoded: str):
    if not multitap_encoded.replace(" ", "").isdecimal():
        return ""
    if "1" in multitap_encoded:
        return ""

    t9_map = {
        "2" : "abc",
        "3" : "def",
        "4" : "ghi",
        "5" : "jkl",
        "6" : "mno",
        "7" : "pqrs",
        "8" : "tuv",
        "9" : "wxyz",
    }
    
    output = ""
    for root, occurences in itertools.groupby(multitap_encoded):
        if root == " ":
            continue

        output += t9_map[root][len(list(occurences))-1]
    return output

if __name__ == "__main__":
    tests = [
        "55544488833",
        "5552884 44",
        "55566688833",
    ]
    for test in tests:
        print(decode_multi_tap(test))