42 lines
704 B
Perl
42 lines
704 B
Perl
package part1;
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use 5.20.0;
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use warnings;
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use List::AllUtils qw/ /;
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use experimental qw/ signatures postderef /;
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sub solution(@seeds) {
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my $last = shift @seeds;
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my $turn = 1;
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my %said;
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for(@seeds) {
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$said{$last} ||= [];
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push $said{$last}->@*, $turn++;
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$last = $_;
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}
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until( $turn == 2020 ) {
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if( !$said{$last} ) {
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$said{$last} = [$turn];
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$last = 0
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} else {
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push $said{$last}->@*, $turn;
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if( $said{$last}->@* > 2 ) {
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shift $said{$last}->@*;
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}
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$last = $said{$last}[-1] - $said{$last}[-2];
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}
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$turn++;
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}
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return $last;
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}
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1;
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