72 lines
1.6 KiB
Perl
72 lines
1.6 KiB
Perl
use 5.20.0;
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use JSON 'to_json';
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use List::AllUtils qw/ all any uniq min part uniq pairgrep any max /;
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my %state = (
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E => 1,
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HM => 1,
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LM => 1,
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HG => 2,
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LG => 3,
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);
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sub freeze { to_json( { @_ }, { canonical => 1 } ) }
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use DDP;
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my $max = 1E99;
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search( 0, \%state, freeze(%state) );
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say $max;
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sub search {
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my( $steps, $state, @history ) = @_;
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say "steps: ", $steps;
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if( all { $_ == 4 } values %$state ) {
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$max = min $max, $steps;
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say "woohoo, found it: $steps, $max";
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return;
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}
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return if $steps + 1 >= $max;
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my $level = $state->{E};
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my @things = grep { $_ ne 'E' and $state->{$_} == $level } keys %$state;
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use Algorithm::Combinatorics qw(combinations);
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$steps++;
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for my $group (2,1) {
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next if @things < $group;
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my $combs = combinations( \@things, $group );
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while( my $c = $combs->next ) {
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I: for my $next_level ( grep { $_ >= 1 and $_ <= 4 } $level + 1, $level - 1 ) {
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my %new_state = ( %$state, map { $_ => $next_level } 'E', @$c );
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my $f = freeze(%new_state);
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if ( any { $_ eq $f } @history ) { next I };
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if ( britzle(%new_state) ) { next I; };
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search( $steps, \%new_state, $f, @history )
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}
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}
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}
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}
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sub britzle {
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my %state = @_;
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my @danger = grep { $state{$_} != $state{ s/M$/G/r } } grep { /.M/ } keys %state;
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for my $level ( uniq map { $state{$_} } @danger ) {
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return 1 if pairgrep { $a =~ /G$/ and $b == $level } %state;
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}
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return 0;
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}
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