题解 | 用两个栈实现队列

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

    int pop() {
        while (!stack1.empty()) {
            auto node = stack1.top();
            stack2.push(node);
            stack1.pop();
        }
        int res = stack2.top();
        stack2.pop();
        while (!stack2.empty()) {
            stack1.push(stack2.top());
            stack2.pop();
        }
        return res;
    }

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