用两个栈实现队列

https://www.nowcoder.com/practice/54275ddae22f475981afa2244dd448c6
思路：将数据从一个栈中捯饬到另一个栈中，模拟队列先进先出。

public class Implementing_queues_with_two_stacks {
    static Stack<Integer> stack1 = new Stack<Integer>();
    static Stack<Integer> stack2 = new Stack<Integer>();
    public static void main(String[] args) {
        push(1);
        push(2);
        System.out.println(pop());
        System.out.println(pop());
    }
    public static void push(int node) {
        stack1.push(node);
    }
    public static int pop() {
        while (!stack1.isEmpty()) {
            stack2.push(stack1.pop());
        }
        int ans = stack2.pop();
        while (!stack2.isEmpty()) {
            stack1.push(stack2.pop());
        }
        return ans;
    }
}