part 2

2018/04/sol2.pl

@@ -0,0 +1,42 @@
+use 5.20.0;
+use warnings;
+
+use List::AllUtils qw/ before after_incl indexes sum pairs pairmap first unpairs /;
+use List::UtilsBy qw/ partition_by max_by /;
+
+use experimental qw/
+    signatures
+    postderef
+/;
+
+my @entries = sort <>;
+
+say $_ for @entries;
+
+my %sleep;
+
+my $guard;
+my $start;
+for ( @entries ) {
+    if( /#(\d+)/ ) { $guard = $1; }
+    elsif( /0?(\d+)\] falls asleep/ ) { $start = $1; }
+    elsif( /0?(\d+)\] wakes/ ) { 
+        push $sleep{$guard}->@*, [ $start, $1 ];
+    }
+}
+
+sub best_time {
+    unpairs
+    max_by { $_->[1] }
+    pairs 
+    pairmap { $a => scalar @$b } partition_by { $_ }  map { $_->[0]..$_->[1]-1 } @_;
+}
+
+use DDP;
+
+my $worst =
+max_by { $_->[2] }
+pairmap { [ $a => best_time( @$b ) ] } %sleep;
+
+p $worst;
+say $worst->[0] * $worst->[1];