Advent of code - Day 15 - Part two

<?php

function readInput(): array
{
    $lines = [];

    $f = fopen( 'php://stdin', 'r' );

    while( $line = fgets( $f ) ) {
        $withOutNewLine = str_replace(PHP_EOL,'',$line);
        if ($withOutNewLine != '') {
            $lines[] = $withOutNewLine;
        }
    }

    fclose($f);

    return $lines;
}

$input = readInput();

$grid = [];

foreach ($input as $line) {
    $grid[] = array_map(fn($item) => intval($item), str_split($line));
}

$grid = expandGrid($grid);

$resp = floodFill(['x' => 0, 'y' => 0], $grid);

echo $resp . PHP_EOL;

function expandGrid($grid)
{
    $w = count($grid[0]);
    $l = count($grid);

    $newW = $w*5;
    $newL = $l*5;

    $newGrid = array_fill(0, $l * 5, array_fill(0, $w * 5, 0));


    for ($i=0; $i < $l; $i++) {
        for ($j=0; $j < $w; $j++) {
            $newGrid[$i][$j] = $grid[$i][$j];
        }
    }

    for ($i=0; $i < $newL; $i++) {
        for ($j=$w; $j < $newW; $j++) {
            $newGrid[$i][$j] = $newGrid[$i][$j-$w] + 1;

            if ($newGrid[$i][$j] > 9) {
                $newGrid[$i][$j] = 1;
            }
        }
    }

    for ($i=$l; $i < $newL; $i++) {
        for ($j=0; $j < $newW; $j++) {
            $newGrid[$i][$j] = $newGrid[$i-$l][$j] + 1;

            if ($newGrid[$i][$j] > 9) {
                $newGrid[$i][$j] = 1;
            }
        }
    }

    return $newGrid;
}

function floodFill($startingPoint, $grid) {
    $visited = array_fill(0, count($grid), array_fill(0, count($grid[0]), PHP_INT_MAX));
    $queue = [$startingPoint];

    $visited[0][0] = 0;

    while (count($queue) > 0) {
        $point = array_shift($queue);
        $y = $point['y'];
        $x = $point['x'];

        if ($y - 1 >= 0) {
            if ($visited[$y -1][$x] > $visited[$y][$x] + $grid[$y-1][$x]) {
                $queue[] =
                    [
                        'y' => $y-1,
                        'x' => $x
                    ];

                $visited[$y -1][$x] = $visited[$y][$x] + $grid[$y-1][$x];
            }
        }
        // down
        if ($y + 1 < count($grid)) {
            if ($visited[$y + 1][$x] > $visited[$y][$x] + $grid[$y+1][$x]) {
                $queue[] = [
                    'y' => $y+1,
                    'x' => $x
                ];
                $visited[$y + 1][$x] = $visited[$y][$x] + $grid[$y+1][$x];
            }
        }
        // left
        if ($x - 1 >= 0) {

            if ($visited[$y][$x-1] > $visited[$y][$x] + $grid[$y][$x-1]) {
                $queue[] = [
                    'y' => $y,
                    'x' => $x-1
                ];
                $visited[$y][$x-1] = $visited[$y][$x] + $grid[$y][$x-1];
            }
        }
        // right
        if ($x + 1 < count($grid[0])) {
            if ($visited[$y][$x+1] > $visited[$y][$x] + $grid[$y][$x+1]) {
                $queue[] = [
                    'y' => $y,
                    'x' => $x+1
                ];
                $visited[$y][$x+1] = $visited[$y][$x] + $grid[$y][$x+1];
            }
        }
    }

    return $visited[count($grid)-1][count($grid[0])-1];
}