How to move contents from one stack to another?

Question

我想将内容从堆栈收件箱移动到发件箱,然后返回发件箱的顶部.但pop的返回类型是void,因此代码抛出一个错误:void值不应该被忽略.

如何移动价值观？

这是代码:

template <class E>
class Queue
{

    private:
        stack<E> inbox;
        stack<E> outbox;

    public:
     void enqueue(E item) {
        inbox.push(item);
    }

    E dequeue() {
        if (outbox.empty()) {
            while (!inbox.empty()) {
                outbox.push(inbox.pop());
            }
        }

        return outbox.pop();
    }

};

Answer 1

它stack::top返回堆栈的顶部.stack::pop只需删除顶部元素而不返回它.

E dequeue() {
    if (outbox.empty()) {
        while (!inbox.empty()) {
            outbox.push(inbox.top());
            inbox.pop();
        }
    }
    E ret = outbox.top();
    outbox.pop();
    return ret;
}