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# 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).

push o(n) other o(1)

{% embed url="<https://leetcode.com/problems/implement-stack-using-queues/solution/>" %}

```java
class MyStack {
    private Queue<Integer> queue;
    /** Initialize your data structure here. */
    public MyStack() {
        queue = new LinkedList<>();
    }
    
    /** Push element x onto stack. */
    public void push(int x) {
        queue.offer(x);
        
        int size = queue.size();
        
        while(size > 1){
            queue.offer(queue.poll());
            size--;
        }
    }
    
    /** 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();
 */
```


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