【剑指offer】9、用两个栈实现队列

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

    int pop() {
        if (stack2.size() == 0)
        {
            while ( stack1.size() > 0){
                int temp = stack1.top();
                stack1.pop();
                stack2.push(temp);
            }
        }
        int head = stack2.top();
        stack2.pop();
        
        return head;
    }

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