算法:用两个栈实现队列

import java.util.Stack;

public class Solution {
    Stack<Integer> inStack = new Stack<>();
    Stack<Integer> outStack = new Stack<>();

    public void push(int node) {
        inStack.push(node);
    }

    public int pop() {
        if(inStack.empty()&&outStack.empty()){
            throw new RuntimeException("Queue is empty!");
        }
        if(outStack.empty()){
            while(!inStack.empty()){
                outStack.push(inStack.pop());
            }
        }
        return outStack.pop();
    }
}