队列

队列可以基于前面的List实现

#include "List.hpp"

template <typename T> class Queue: public List<T> {
public:
    void enqueue(T const& e){
        this->insertAsLast(e);
    }
    
    T dequeue(){
        return this->remove(this->first());
    }
    
    T& front(){
        return this->first()->data;
    }
};