<?php

$input = file('input', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
$input = array_map(fn($line) => explode(' | ', $line), $input);
$sum = 0;
foreach ($input as $digits) {
    $sum += decodeNumbers(explode(' ', $digits[0]), explode(' ', $digits[1]));
}
echo $sum; //961734

function decodeNumbers($inputArray, $displayedNumbers)
{
    foreach ($inputArray as &$digits) {
        $digits = str_split($digits);
        sort($digits);
    }

    foreach ($displayedNumbers as &$displayedNumber) {
        $displayedNumber = str_split($displayedNumber);
        sort($displayedNumber);
    }

    $numbers = array_fill(0, 9, null);

    $numbers[1] = current(array_filter($inputArray, fn($element) => count($element) == 2));
    unset($inputArray[array_search($numbers[1], $inputArray)]);
    $numbers[4] = current(array_filter($inputArray, fn($element) => count($element) == 4));
    unset($inputArray[array_search($numbers[4], $inputArray)]);
    $numbers[7] = current(array_filter($inputArray, fn($element) => count($element) == 3));
    unset($inputArray[array_search($numbers[7], $inputArray)]);
    $numbers[8] = current(array_filter($inputArray, fn($element) => count($element) == 7));
    unset($inputArray[array_search($numbers[8], $inputArray)]);
    $numbers[9] = current(array_filter($inputArray, fn($element) => count($element) == 6 && count(array_diff($element, $numbers[4])) == 2));
    unset($inputArray[array_search($numbers[9], $inputArray)]);
    $numbers[0] = current(array_filter($inputArray, fn($element) => count($element) == 6 && count(array_diff($element, $numbers[1])) == 4));
    unset($inputArray[array_search($numbers[0], $inputArray)]);
    $numbers[6] = current(array_filter($inputArray, fn($element) => count($element) == 6));
    unset($inputArray[array_search($numbers[6], $inputArray)]);
    $numbers[5] = current(array_filter($inputArray, fn($element) => count($element) == 5 && count(array_diff($numbers[6], $element)) == 1));
    unset($inputArray[array_search($numbers[5], $inputArray)]);
    $numbers[2] = current(array_filter($inputArray, fn($element) => count($element) == 5 && count(array_diff($numbers[5], $element)) == 2));
    unset($inputArray[array_search($numbers[2], $inputArray)]);
    $numbers[3] = current(array_filter($inputArray, fn($element) => count($element) == 5));
    unset($inputArray[array_search($numbers[3], $inputArray)]);

    $result = '';
    foreach ($displayedNumbers as $number) {
        $result .= array_search($number, $numbers);
    }
    return (int)$result;
}