您的位置:首页 > 产品设计 > UI/UE

Implement Stack using Queues

2015-08-08 22:11 369 查看
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 {
    Queue<Integer> queue;
    
    public MyStack(){
        this.queue = new LinkedList<Integer>();
    }
    
    // Push element x onto stack.
    public void push(int x) {
        queue.add(x);
        for(int i = 0; i < queue.size()-1; i++){
            queue.add(queue.poll());
        }
    }

    // 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();
    }
}
内容来自用户分享和网络整理,不保证内容的准确性,如有侵权内容,可联系管理员处理 点击这里给我发消息
标签: