题目:
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
, andis 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).
题意:用queue来模拟stack,用queue的基本操作
思路:比较简单,用两个queue来进行即可,一个作为模拟的stack存储,一个运来转换中间的操作数字
代码:
class MyStack { LinkedList<Integer> queue = new LinkedList<Integer>(); LinkedList<Integer> temp = new LinkedList<Integer>(); // Push element x onto stack. public void push(int x) { while(!queue.isEmpty()){ temp.offer(queue.poll()); } queue.offer(x); while(!temp.isEmpty()){ queue.offer(temp.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(); } }
时间: 2024-10-24 03:01:58