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sub binary-partition(@code, $from is copy, $to is copy, $lower, $upper --> Int) {
for @code[0..*-1] {
when $lower { $to = ($from + $to) div 2 }
when $upper { $from = (($from + $to) div 2) + 1 }
}
return @code[*-1] eq $lower ?? $from !! $to;
}
sub row(@code) {
binary-partition(@code, 0, 127, 'F', 'B')
}
sub column(@code --> Int) {
binary-partition(@code, 0, 7, 'L', 'R')
}
sub get-id($input) {
my $row = row($input.comb[0..^7]);
my $column = column($input.comb[7..^10]);
($row * 8) + $column
}
multi sub MAIN('part1', $file) {
say $file.IO.lines.map(*.&get-id).max;
}
multi sub MAIN('part2', $file) {
my $gap = $file.IO.lines.map(*.&get-id).sort.rotor(2=>-1).grep(
-> ($a, $b) {
$a+1 != $b
}
).head;
say $gap.head + 1;
}
multi sub MAIN('test') {
use Test;
is row(<F B F B B F F>), 44, 'row';
is column(<R L R>), 5, 'column';
is get-id('BFFFBBFRRR'), 567, 'example 1';
is get-id('FFFBBBFRRR'), 119, 'example 2';
is get-id('BBFFBBFRLL'), 820, 'example 3';
}
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