leetcode-232

 Implement Queue using Stacks

Implement the following operations of a queue using stacks.

• push(x) -- Push element x to the back of queue.
• pop() -- Removes the element from in front of queue.
• peek() -- Get the front element.
• empty() -- Return whether the queue is empty.

题目的大概意思就是让我们用栈实现队列的相关功能。Stack是java里面已经写好的栈类可以直接使用。

java代码:

public class MyQueue{
	Stack<Integer> queue=new Stack<Integer>();
	public void push(int x){
		Stack<Integer> temp=new Stack<Integer>();
		while(!queue.empty()){
			temp.push(queue.pop());
		}
		queue.push(x);
		while(!temp.empty()){
			queue.push(temp.pop());
		}
	}
	public int pop(){
		return queue.pop();
	}
	public int peek(){
		return queue.peek();
	}
	public boolean empty(){
		return queue.empty();
	}
	
}