Largest product in a grid: Difference between revisions

=== Generalized ===

Handles non-square input (both narrow and wide).

<lang perl>use strict;

use warnings;

use feature 'say';

use List::AllUtils <max reduce>;

my $input = <<~END;

08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08

49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00

81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65

52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91

22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80

24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50

32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70

67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21

24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72

21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95

78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92

16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57

86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58

19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40

04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66

88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69

04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36

20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16

20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54

01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48

END

my(@m,@mt);

push @m, [ split /\s+/, s/\b0//gr ] for split "\n", $input;

for my $j (0..$#{$m[0]}) { push @mt, [ map $_->[$j], @m ] } # transpose

sub max_products {

my($terms,@matrix) = @_;

my @products;

my $columns = 1 + $#{$matrix[0]};

for my $row (@matrix) {

map { push @products, reduce { $a * $b } @$row[ $_ .. $_+$terms-1 ] } 0 .. $columns-$terms;

}

max @products

}

say "Largest product of $_ adjacent elements: " . max max_products($_,@m), max_products($_,@mt) for 1..6;</lang>

{{out}}

<pre>Largest product of 1 adjacent elements: 99

Largest product of 2 adjacent elements: 9215

Largest product of 3 adjacent elements: 776776

Largest product of 4 adjacent elements: 51267216

Largest product of 5 adjacent elements: 2326829868

Largest product of 6 adjacent elements: 188210512710</pre>