用两个栈实现队列

class Solution
{
public:
    void push(int node) {
        stack1.push(node);
    }

    int pop() {
        int elem;
        if(stack2.empty())
        {
            while(stack1.size())
            //while(!stack1.empty())
            {
                elem = stack1.top();
                stack2.push(elem);
                stack1.pop();
            }
        }
        int a = stack2.top();
        stack2.pop();
        return a;
    
    }

private:
    stack<int> stack1;
    stack<int> stack2;
};