Task_8_Largest_product_in_a_series.py

"""
https://projecteuler.net/problem=8

The four adjacent digits in the 1000-digit number that have the greatest product are 9 × 9 × 8 × 9 = 5832.
Find the thirteen adjacent digits in the 1000-digit number that have the greatest product.
What is the value of this product?
"""
from functools import reduce
from operator import mul
from time import time

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


def find_greatest_product(d):
    length_of_number = len(d)
    p_start = 0  # pointer start
    p_end = 13  # pointer end
    max_digit = 0

    while p_end < length_of_number:
        new_digit = reduce(mul, [int(x) for x in d[p_start:p_end]])

        if new_digit > max_digit:
            max_digit = new_digit

        p_start += 1
        p_end += 1

    return max_digit


if __name__ == '__main__':
    start = time()

    # Prepare 1000-digit number, remove spaces
    digit = ''.join(digit.split())

    print(f'Result: {find_greatest_product(digit)}')
    print(f'Time: {time() - start}')