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euler0008.py
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euler0008.py
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#!/usr/bin/python
r"""Largest product in a series
The four adjacent digits in the 1000-digit number that have the greatest
product are $9\times 9\times 8\times 9 = 5832$.
73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450
Find the thirteen adjacent digits in the 1000-digit number that have the
greatest product. What is the value of this product?"""
from eulerlib import product
__tags__ = ['digits', 'maximization']
s = ''.join(l.strip() for l in __doc__.splitlines()[5:-3])
seqlen = 13
def uphill(start):
while start+seqlen < len(s) and ('0' in s[start:start+seqlen]
or s[start] < s[start+seqlen]):
start += 1
return start
def downhill(start):
while start+seqlen < len(s) and s[start] >= s[start+seqlen]:
start += 1
return start
def seqprod(start):
return product(int(c) for c in s[start:start+seqlen])
def solve():
i = uphill(0)
maximum = seqprod(i)
while i+seqlen < len(s):
i = uphill(downhill(i))
maximum = max(maximum, seqprod(i))
maximum = max(maximum, seqprod(i))
return maximum
if __name__ == '__main__':
print solve()