Advent of Code 2025 day 3

aoc03

#!/usr/bin/env raku
use v6.d;
$*OUT.out-buffer = False;   # Autoflush

# Advent of Code 2025 day 3 -- https://adventofcode.com/2025/day/3

unit sub MAIN(IO() $inputfile where *.f = 'aoc03.input', Bool :v($verbose) = False);

sub joltage($bank, $count=2)
{
    # Find the first occurrence of the highest digit in the bank
    # (excluding the final count-1 ones)
    my $digit1 = $bank.substr(0, *-($count-1)).comb.max;
    my $pos1 = $bank.index($digit1);

    # If there are more batteries to switch on, do so recursively
    my $joltage = $count > 1 ?? $digit1 ~ joltage($bank.substr($pos1+1), $count-1)
                             !! $digit1;

    say '#' x $count, " $bank: $joltage" if $verbose;
    return $joltage;
}

my @banks = $inputfile.lines;
say "Part one: ", @banks».&joltage.sum;
say "Part two: ", @banks».&joltage(12).sum;