advent_of_code_2019/day_10/part_1.php

<?php

include 'functions.php';

$rows = explode("\n", file_get_contents('input.txt'));

// Make the list of asteroids coordinates
$asteroids = array_flatten(
    array_filter(
        array_map(static function($row, $i) {
            return array_filter(array_map(static function($col, $j) use ($i) {
                if ($col === '#') {
                    return sprintf('%s,%s', $i, $j);
                }

                return null;
            }, str_split($row), range(0, strlen($row))));
        }, $rows, range(0, count($rows)))
    )
);

$asteroid_count = [];
foreach ($asteroids as $asteroid_base) {
    $count = 0;
    foreach ($asteroids as $asteroid_target) {
        if ($asteroid_base === $asteroid_target) {
            continue;
        }

        $points_base = explode(',', $asteroid_base);
        $points_target = explode(',', $asteroid_target);

        $points = getPointsBetween($points_base[0], $points_base[1], $points_target[0], $points_target[1]);

        $add_point = true;
        foreach ($points as $point) {
            if ($point === $asteroid_base || $point === $asteroid_target) {
                continue;
            }
            if (in_array($point, $asteroids)) {
                $add_point = false;
                break;
            }
        }
        if ($add_point) {
            $count++;
        }
    }
    $asteroid_count[$asteroid_base] = $count;
}

arsort($asteroid_count);
var_dump($asteroid_count);
echo current($asteroid_count);