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Find the greatest product of five consecutive digits in the 1000-digit number.

Problem Statement

Find the greatest product of five consecutive digits in the 1000-digit number.

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

Notes

An interesting side note here is how does one specify a 1000 digit number. In this case I chose to use the python """ string delimiter to specify a multiline string exactly as described in the problem statement. However such a string has embedded \n characters which need to be removed. (lines 1 to 22).

Lines 31 and 32 create a sequence of all the substrings of 5 consecutive digits in the above number. Lines 29 and 30 compute the product of all the numbers that form the substring. Line 28 represents the tuple of the substring followed by the product. The reduce function on lines 24 to 26 (which gets intialised with the initial data on line 33) then continuously selects the tuple with the maximum product. The final '[1]' indexing operation on line 33 then just selects the product from the number product tuple selected by the earlier reduce function.

Solution

strnum = """
73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450
""".replace('\n','')

print reduce(
        lambda x,(y,z) : 
            x[1] < z and (y,z) 
            or x,tuple(
                (substr,
                 reduce(
                    lambda x,y : x * int(y), substr, 1))
                for substr in (strnum[i:i+5] 
                    for i in xrange(len(strnum)-4))),
            ('',0))[1]

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