function step($grid)
{
$new = $grid;
for ($j = 0; $j < 100; $j++) {
for ($k = 0; $k < 100; $k++) {
$on = countOn($grid, $j, $k);
if ($grid[$j][$k] === 0 && $on === 3) {
$new[$j][$k] = 1;
} else {
if ($grid[$j][$k] === 1 && $on != 3 && $on != 2) {
$new[$j][$k] = 0;
}
}
}
}
return $new;
}
$file = file('input', FILE_IGNORE_NEW_LINES);
$zeroToThousand = range(0, 999);
$lights = array_fill_keys($zeroToThousand, array_fill_keys($zeroToThousand, 0));
foreach ($file as $cmd) {
preg_match('/([a-z ]{4,9})([0-9]{1,3}\\,[0-9]{1,3}) through ([0-9]{1,3}\\,[0-9]{1,3})/', $cmd, $matches);
array_shift($matches);
list($command, $startCoords, $endCoords) = $matches;
$command = trim($command);
$startCoords = explode(',', $startCoords);
$endCoords = explode(',', $endCoords);
$lightsToSet = getCoordsBetweenInRectangle($startCoords, $endCoords);
foreach ($lightsToSet as $light) {
$lights[$light[0]][$light[1]] = whatSetTo($command, $light);
}
}
echo countOn($lights) . PHP_EOL;
function getCoordsBetweenInRectangle($startCoords, $endCoords)
{
$coords = [];
for ($row = $startCoords[0]; $row <= $endCoords[0]; $row++) {
for ($column = $startCoords[1]; $column <= $endCoords[1]; $column++) {
$coords[] = [$row, $column];
}
}
return $coords;
}
function whatSetTo($command, $coords)
{
global $lights;
switch ($command) {
case 'turn on':
