算法-栈stack-用栈实现队列-Leetcode232

class MyQueue {

    Stack<Integer> stack1 = new Stack<>();
    Stack<Integer> stack2 = new Stack<>();

    /**
     * Initialize your data structure here.
     */
    public MyQueue() {

    }

    /**
     * Push element x to the back of queue.
     */
    public void push(int x) {
        stack1.push(x);
    }

    /**
     * Removes the element from in front of queue and returns that element.
     */
    public int pop() {
        while (!stack1.empty()) {
            stack2.push(stack1.pop());
        }
        int result = stack2.pop();
        while (!stack2.empty()) {
            stack1.push(stack2.pop());
        }
        return result;
    }

    /**
     * Get the front element.
     */
    public int peek() {
        while (!stack1.empty()) {
            stack2.push(stack1.pop());
        }
        int result = stack2.peek();
        while (!stack2.empty()) {
            stack1.push(stack2.pop());
        }
        return result;
    }

    /**
     * Returns whether the queue is empty.
     */
    public boolean empty() {
        return stack1.empty();
    }
}