# Implement Stack using Queues

Implement the following operations of a stack using queues.

* push(x) -- Push element x onto stack.
* pop() -- Removes the element on top of the stack.
* top() -- Get the top element.
* empty() -- Return whether the stack is empty.

**Example:**

```
MyStack stack = new MyStack();

stack.push(1);
stack.push(2);  
stack.top();   // returns 2
stack.pop();   // returns 2
stack.empty(); // returns false
```

**Notes:**

* You must use only standard operations of a queue -- which means only `push to back`, `peek/pop from front`

  , `size`, and `is empty`operations are valid.
* Depending on your language, queue may not be supported natively. You may simulate a queue by using a list or deque (double-ended queue), as long as you use only standard operations of a queue.
* You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).

## Analysis

<https://leetcode.com/articles/implement-stack-using-queues/>

## Solution

One Queue Implementation

```java
class MyStack {
    private Queue<Integer> queue;
    /** Initialize your data structure here. */
    public MyStack() {
        queue = new LinkedList<Integer> (); 
    }

    /** Push element x onto stack. */
    public void push(int x) {
        queue.add(x);
        for (int i = 1; i < queue.size(); i++) {
            queue.add(queue.poll());
        }
    }

    /** Removes the element on top of the stack and returns that element. */
    public int pop() {
       return queue.poll(); 
    }

    /** Get the top element. */
    public int top() {
       return queue.peek(); 
    }

    /** Returns whether the stack is empty. */
    public boolean empty() {
       return queue.isEmpty(); 
    }
}

/**
 * Your MyStack object will be instantiated and called as such:
 * MyStack obj = new MyStack();
 * obj.push(x);
 * int param_2 = obj.pop();
 * int param_3 = obj.top();
 * boolean param_4 = obj.empty();
 */
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://aaronice.gitbook.io/lintcode/queue/implement-stack-using-queues.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.