8.py

import re
from typing import List

from utils import multiply


def max_adjacent_digits_products(*,
                                 digits: List[int],
                                 adjacent_digits_count: int) -> int:
    adjacent_digits = list(digits[start:start + adjacent_digits_count]
                           for start in range(len(digits)
                                              - adjacent_digits_count + 1))
    adjacent_digits_products = map(multiply, adjacent_digits)
    return max(adjacent_digits_products)


def largest_series_product(*,
                           number_str: str,
                           adjacent_digits_count: int) -> int:
    non_zero_digits_series = [
        list(map(int, non_zero_digits_str))
        # digits sequences with zero cannot give maximum multiply
        for non_zero_digits_str in re.split('0+', number_str)
        # skipping too short digits sequences
        if len(non_zero_digits_str) >= adjacent_digits_count]
    max_adjacent_digits_series_products = (
        max_adjacent_digits_products(digits=non_zero_digits,
                                     adjacent_digits_count=adjacent_digits_count)
        for non_zero_digits in non_zero_digits_series)
    return max(max_adjacent_digits_series_products,
               # for number strings filled with zeros
               default=0)


number_str = (
    "73167176531330624919225119674426574742355349194934"
    "96983520312774506326239578318016984801869478851843"
    "85861560789112949495459501737958331952853208805511"
    "12540698747158523863050715693290963295227443043557"
    "66896648950445244523161731856403098711121722383113"
    "62229893423380308135336276614282806444486645238749"
    "30358907296290491560440772390713810515859307960866"
    "70172427121883998797908792274921901699720888093776"
    "65727333001053367881220235421809751254540594752243"
    "52584907711670556013604839586446706324415722155397"
    "53697817977846174064955149290862569321978468622482"
    "83972241375657056057490261407972968652414535100474"
    "82166370484403199890008895243450658541227588666881"
    "16427171479924442928230863465674813919123162824586"
    "17866458359124566529476545682848912883142607690042"
    "24219022671055626321111109370544217506941658960408"
    "07198403850962455444362981230987879927244284909188"
    "84580156166097919133875499200524063689912560717606"
    "05886116467109405077541002256983155200055935729725"
    "71636269561882670428252483600823257530420752963450")

assert largest_series_product(number_str=number_str,
                              adjacent_digits_count=4) == 5_832
assert largest_series_product(number_str=number_str,
                              adjacent_digits_count=13) == 23_514_624_000