38 lines
610 B
Perl
38 lines
610 B
Perl
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package part1;
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use 5.20.0;
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use warnings;
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use experimental qw/
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signatures
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postderef
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/;
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sub solution($n, $entries) {
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my @numbers = split "\n", $entries;
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my %seen;
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my @previous;
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# prime the pump
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while( @previous < $n ) {
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my $n = shift @numbers;
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$seen{$n + $_}++ for @previous;
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push @previous, $n;
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}
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while(my $next = shift @numbers) {
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return $next unless $seen{$next};
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my $goner = shift @previous;
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$seen{$goner + $_}-- for @previous;
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$seen{$next + $_}++ for @previous;
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push @previous, $next;
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}
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}
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1;
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