Advent of Code 2024 - Day 1

day_1_part_1.php

<?php

declare(strict_types=1);

$input = <<<'EOD'
3   4
4   3
2   5
1   3
3   9
3   3
EOD;

$leftList = [];
$rightList = [];
$differences = [];

$rows = explode("\n", $input);

foreach ($rows as $row) {
    [$left, $right] = explode('   ', $row);
    $leftList[] = (int) $left;
    $rightList[] = (int) $right;
}

sort($leftList);
sort($rightList);

foreach ($leftList as $index => $left) {
    $differences[] = abs($left - $rightList[$index]);
}

return array_sum($differences);

day_1_part_2.php

<?php

declare(strict_types=1);

$input = <<<'EOD'
3   4
4   3
2   5
1   3
3   9
3   3
EOD;

$leftList = [];
$rightList = [];
$score = [];

$rows = explode("\n", $input);

foreach ($rows as $row) {
    [$left, $right] = explode('   ', $row);
    $leftList[] = (int) $left;
    $rightList[] = (int) $right;
}

$count = array_count_values($rightList);

foreach ($leftList as $value) {
    $score[] = \array_key_exists($value, $count) ? $count[$value] * $value : 0;
}

return array_sum($score);