225. Implement Stack using Queues

发表于 | 分类于 ， | 阅读次数:

Total Accepted: 31239
Total Submissions: 102745
Difficulty: Easy

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).

Java:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
class MyStack {
    private Deque<Integer> queue = new ArrayDeque<>();

    // Push element x onto stack.
    public void push(int x) {
        queue.add(x);
    }

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

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

    // Return whether the stack is empty.
    public boolean empty() {
        return queue.size()==0;
    }
}

打个小广告

欢迎加入我的小专栏「基你太美」一起学习。