剑指Offer总结——用两个栈实现队列

class Solution
{
public:
    void push(int node) {
        stack2.push(node);
    }

    int pop() {
        if(stack1.empty()){
            while(!stack2.empty()) {
                stack1.push(stack2.top());
                stack2.pop();
            }
        }
        int val = stack1.top();
        stack1.pop();
        return val;
    }

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