Advent of Code 2023 - Part 6

part6.php

<?php

final readonly class Boat
{
    public function __construct(
        private int $time,
        private int $record,
    ) {
    }

    public function options(): int
    {
        $ways = 0;

        for ($hold = 0; $hold <= $this->time; $hold++) {
            $race = $this->time - $hold;
            $distance = $hold * $race;

            if ($distance > $this->record) {
                $ways++;
            }
        }

        return $ways;
    }
}

$boats = [
    new Boat(7, 9),
    new Boat(15, 40),
    new Boat(30, 200),
];
$single = new Boat(71530, 940200);

$options = array_map(static fn (Boat $boat): int => $boat->options(), $boats);

$part1 = array_reduce($options, static fn (int $multiplied, int $options) => $multiplied * $options, 1);
$part2 = $single->options();

$result = [$part1, $part2];