# 0225. Implement Stack using Queues

https://leetcode.com/problems/implement-stack-using-queues

## Description

Implement a last-in-first-out (LIFO) stack using only two queues. The implemented stack should support all the functions of a normal stack (`push`, `top`, `pop`, and `empty`).

Implement the `MyStack` class:

* `void push(int x)` Pushes element x to the top of the stack.
* `int pop()` Removes the element on the top of the stack and returns it.
* `int top()` Returns the element on the top of the stack.
* `boolean empty()` Returns `true` if the stack is empty, `false` otherwise.

**Notes:**

* You must use **only** standard operations of a queue, which means that only `push to back`, `peek/pop from front`, `size` and `is empty` operations are valid.
* Depending on your language, the queue may not be supported natively. You may simulate a queue using a list or deque (double-ended queue) as long as you use only a queue's standard operations.

**Example 1:**

```
**Input**
["MyStack", "push", "push", "top", "pop", "empty"]
[[], [1], [2], [], [], []]
**Output**
[null, null, null, 2, 2, false]
**Explanation**
MyStack myStack = new MyStack();
myStack.push(1);
myStack.push(2);
myStack.top(); // return 2
myStack.pop(); // return 2
myStack.empty(); // return False
```

**Constraints:**

* `1 <= x <= 9`
* At most `100` calls will be made to `push`, `pop`, `top`, and `empty`.
* All the calls to `pop` and `top` are valid.

**Follow-up:** Can you implement the stack using only one queue?

## ac

```java
```
