adventofcode/2020/10/part2.pm

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2021-12-05 16:51:21 +00:00
package part2;
use 5.20.0;
use warnings;
use List::AllUtils qw/ /;
require './part1.pm';
use experimental qw/ signatures postderef /;
use Memoize;
memoize('ways');
sub ways($first, @rest) {
return 1 unless @rest;
my $ways = 0;
while( my $next = shift @rest ) {
last if $next - $first > 3;
$ways += ways($next, @rest);
}
return $ways;
}
sub solution(@lines) {
@lines = sort {$a<=>$b}@lines;
unshift @lines, 0;
push @lines, $lines[-1] + 3;
return ways(@lines);
}
1;