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<?php
declare(strict_types=1);
namespace leetcode;
class ImplementQueueUsingStacks
{
private array $cache = [];
private array $stack = [];
private ?int $front;
public function push(int $value): void
if (empty($this->stack)) {
$this->front = $value;
}
while (!empty($this->stack)) {
$this->cache[] = array_shift($this->stack);
$this->cache[] = $value;
while (!empty($this->cache)) {
$this->stack[] = array_shift($this->cache);
public function pop(): ?int
$value = array_shift($this->stack);
if (!empty($this->stack)) {
$this->front = current($this->stack);
return $value;
public function peek(): ?int
return null;
return $this->front;
public function empty(): bool
return count($this->stack) === 0 && count($this->cache) === 0;
imajinyun /
leetcode-php
