AOC-2024

day1.php

<?php

function csvToArray($csvString, $delimiter = ",", $lineBreak = "\n")
{
    $csvArray = [];
    $rows = str_getcsv($csvString, $lineBreak); // Parses the rows. Treats the rows as a CSV with \n as a delimiter
    foreach ($rows as $row) {
        $csvArray[] = str_getcsv($row, $delimiter); // Parses individual rows. Now treats a row as a regular CSV with ',' as a delimiter
    }
    return $csvArray;
}

$left = [];
$right = [];

$input = <<<INPUT
3   4
4   3
2   5
1   3
3   9
3   3
INPUT;

$input = str_replace(subject: $input, search: "   ", replace: ",");

// dd($input);
$rows = csvToArray($input);

$left = array_column($rows, 0);
$right = array_column($rows, 1);

function getDistance($left, $right)
{
    sort($left);
    sort($right);

    $distance = 0;
    foreach ($left as $i => $v) {
        $distance += abs($left[$i] - $right[$i]);
    }
}

function getSimilarity($left, $right)
{
    $return = 0;
    $rightCount = [];
    foreach ($right as $num) {
        if (!isset($rightCount[$num])) {
            $rightCount[$num] = 0;
        }
        $rightCount[$num]++;
    }

    foreach ($left as $num) {
        $return += $num * ($rightCount[$num] ?? 0);
    }

    return $return;
}

return getSimilarity($left, $right);