LeetCode225 Implement Stack using Queues
阿新 • • 發佈:2018-12-22
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.
class MyStack { Queue<Integer> queue; /** Initialize your data structure here. */ 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 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(); */