Implement Stack using Queues

最新推荐文章于 2024-07-08 11:43:44 发布

最新推荐文章于 2024-07-08 11:43:44 发布 · 152 阅读

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本文介绍了一种使用队列来实现栈数据结构的方法。通过定义一个名为MyStack的类，该类利用LinkedList作为底层实现，提供了push、pop、top和empty等栈的基本操作。文章详细解释了如何通过队列的标准操作实现这些功能。

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.

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).

class MyStack {
	private LinkedList<Integer> queue = new LinkedList<>();
    // Push element x onto stack.
    public void push(int x) {
        queue.offer(x);
        int size = queue.size() - 1;
        while (size > 0) {
        	queue.offer(queue.poll());
        	size--;
        }
    }

    // Removes the element on top of the stack.
    public void pop() {
    	queue.poll();
    }

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

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