题解 | #用两个栈实现队列#

//定义两个栈，保证一个只进，一个只出
class Solution
{
public:
    void push(int node) {{
            stack1.push(node);
        }
        
    }

    int pop() {
        if (stack2.empty()&&stack1.empty()) {
            return -1;
        }
        else if (stack2.empty()) {
            while (!stack1.empty()) {
                int num=stack1.top();
                stack2.push(num);
                stack1.pop();
            }
            int re =stack2.top();
            stack2.pop();
            return re;
        }
        else {
            int re =stack2.top();
            stack2.pop();
            return re;
        }
    }

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