package com.chanmufeng.codingInterviewGuide.stackAndQueue_10;

import java.util.Stack;

/**
 * 用两个栈实现队列功能
 */
public class StackQueue {
    private static Stack<Integer> pushStack;
    private static Stack<Integer> popStack;

    public StackQueue() {
        pushStack = new Stack<>();
        popStack = new Stack<>();
    }

    public static void enqueue(int newNum) {
        pushStack.push(newNum);
    }

    public static int poll() {
        if (pushStack.isEmpty() && popStack.isEmpty()) {
            throw new RuntimeException("queue is empty");
        } else if (popStack.isEmpty()) {
            while (!pushStack.isEmpty()) {
                popStack.push(pushStack.pop());
            }
        }
        return popStack.pop();
    }

    public static int peek() {
        if (pushStack.isEmpty() && popStack.isEmpty()) {
            throw new RuntimeException("queue is empty");
        } else if (popStack.isEmpty()) {
            while (!pushStack.isEmpty()) {
                popStack.push(pushStack.pop());
            }
        }
        return popStack.peek();
    }

    public static void main(String[] args) {

    }
}