牛客网-《剑指offer》-用两个栈实现队列

题目：http://www.nowcoder.com/practice/54275ddae22f475981afa2244dd448c6

C++

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

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

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