cozylife/hackfastalgos

<?HH
/**
 * Hack Fast Algos
 *
 * Implementation of a stack
 * @Learn more @link https://en.wikipedia.org/wiki/Stack_(abstract_data_type)
 */

namespace HackFastAlgos\DataStructure;

class StackInvalidIndexException extends \Exception{}

class Stack implements \Countable
{
    private Vector<T> $stackData = Vector{};

    public function count() : int
    {
        return $this->stackData->count();
    }

    public function push<T>(T $item)
    {
        $this->stackData[] = $item;
    }

    public function pop<T>() : T
    {
        // Manual pop
        $count = $this->stackData->count();

        if ($count === 0) {
            throw new StackInvalidIndexException();
        }

        $last = $this->stackData[$count-1];
        $this->stackData->removeKey($count-1);

        return $last;
    }
}