Shlomi Fish <shlo...@shlomifish.org> writes:
> Hi all!
>
> Resending because the original message does not appear to have arrived at the
> list.
>
> =====
>
> Hi Derrick,
>
> On Tue, 16 May 2017 14:01:34 +0800
> derr...@thecopes.me wrote:
>
>> Hi All,
>>
>> I am working on problem #8 of the euler project. see below.
>>
>>
>> I have the below solution below for this which works fine but gives me the
>> wrong answer. I checked shlomifish's solution on github and his is similar to
>> mine, more elegant since he uses "map", but he gets a different answer. I
>> feel like I have some basic misunderstanding about how something should work.
>> Or maybe I am misunderstanding the problem. Thanks in advance for any push in
>> the right direction. see my solution below.
>>
>> Derrick
>>
>> #! /usr/bin/env perl
>>
>> use strict;
>> use warnings;
>> use 5.024;
>> use List::Util qw(max product);
>>
>> my $totalmax = 0;
>>
>> while ( my $numbline = <DATA> ) {
>> chomp $numbline;
>> my @numbline = split //, $numbline;
>
> You're processing the input number line-by-line, but it's one whole number and
> the products may span across more than one line. You need to slurp it and
> prepare an array of digits.
Isn't it more efficient to put all the digits into a string rather than
into an array and use substr()?
With a bit extra ado you could omit, for the sake of verifyability (It
doesn't matter in which order you do the multiplications of the adjacent
digits as long as they are adjacent.):
#!/usr/bin/perl
use strict;
use warnings;
my $data = "
73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450
";
$data =~ s/\n//g;
my $adjacency = 13;
my $maxprod = 0;
my $start = 0;
my $end = length($data) - $adjacency;
while($start < $end) {
my $adjunct = 1;
my $prod = substr($data, $start, 1);
print "$prod";
while($adjunct < $adjacency) {
my $ad = substr($data, $start + $adjunct, 1);
print " * $ad";
$prod *= $ad;
$adjunct++;
}
print " = $prod\n";
$maxprod = $prod if($maxprod < $prod);
$start++;
}
print "The largest product of $adjacency adjacent numbers is $maxprod.\n";
exit 0;
Is this supposed to be a programming exercise? It's a purely
mathematical one to me.
>
>> say "@numbline ";
>> my @product = ();
>> for (0..$#numbline - 13) {
>
> This should be "@numbline - 13" - an off-by-one error.
>
> Regards,
>
> Shlomi Fish
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