模板链接列表编译错误

我正在为学校制定一个计划。它是一个使用模板的链接列表。

我有一个抽象基类：

#pragma once
#include <string>
using namespace std;
template<class T>
class LinkedListInterface
{
public:
    LinkedListInterface(void){};
    virtual ~LinkedListInterface(void){};

    virtual void insertHead(T value) = 0;

    virtual void insertTail(T value) = 0;

    virtual void insertAfter(T value, T insertionNode) = 0;

    virtual void remove(T value) = 0;

    virtual void clear() = 0;

    virtual T at(int index) = 0;

    virtual int size() = 0;
};

我从中派生出一个类：

/* Linklist.h
 *
 *  Created on: Oct 4, 2014
  *   
  */
 #ifndef LINKLIST_H_
 #define LINKLIST_H_
 #include <iostream>
 #include "LinkedListInterface.h"
 template<class T>
 class Linklist: public LinkedListInterface<T> {
 private:
     struct _node
         {
           T val;
           Linklist *next;
         };
         struct _node node ;
        Linklist *root = NULL;
        Linklist *tail = NULL;
        int _size = 0;
        int finddup(T value);
 public:
    Linklist();
    virtual ~Linklist();

     void insertHead(T value);
      void insertTail(T value);

         void insertAfter(T value, T insertionNode);

         void remove(T value);

         void clear();

         T at(int index);

         int size();
 };
 #endif /* LINKLIST_H_ */

链接列表.cpp

 /*
  * Linklist.cpp
  *
  *  Created on: Oct 4, 2014
  *      
  */
 #include "Linklist.h"
 template<class T>
 Linklist<T>::Linklist()
 {
    // TODO Auto-generated constructor stub
 }
 template<class T>
 Linklist<T>::~Linklist()
 {
    // TODO Auto-generated destructor stub
 }
 template<class T>
 int Linklist<T>::finddup(T value)
 {
    Linklist *tmp = root;
    while (tmp)
    {
        if (tmp->node.val == value)
        {
            return 1;
        }
    }
    return 0;
 }

 template<class T>
 void Linklist<T>::insertHead(T value)
 {
    Linklist *tmp = root;
    if (finddup(value))
    {
        return;
    }
    else
    {
        if (!root)
        {
            root = new Linklist<T>();
            root->val = value;
            root->next = NULL;
            tail = root;
            _size++;
        }
        else
        {
            Linklist *newr = new Linklist<T>();
            newr->node.val = value;
            newr->node.next = root;
            root = &newr;
            _size++;
        }
    }
 }

 template<class T>
 void Linklist<T>::insertTail(T value)
 {
    Linklist *tmp = root;
    if (finddup(value))
    {
        return;
    }
    else
    {
        if (!tail)
        {
            tail = new Linklist<T>();
            tail->val = value;
            tail->next = NULL;
            root = tail;
            _size++;
        }
        else
        {
            Linklist *newr = new Linklist<T>();
            newr->node.val = value;
            newr->node.next = NULL;
            tail->node.next = &newr;
            tail = &newr;
            _size++;
        }
    }
 }

 template<class T>
 void Linklist<T>::insertAfter(T value, T insertionNode)
 {
    if (finddup(value))
    {
        return;
    }
    else
    {
        Linklist *tmp = root;
        while (tmp)
        {
            if (tmp->node.val == insertionNode)
            {
                Linklist *newr = new Linklist<T>();
                newr->node.val = value;
                 newr->node.next = tmp->node.next;
                 tmp->node.next = &newr;
                 _size++;
                 break;
             }
             else
                 tmp = tmp->node.next;
         }
     }
 }

 template<class T>
 void Linklist<T>::remove(T value)
 {
    Linklist *prev = NULL, *active = NULL;
    if (!root)
        std::cout << "List is empty" << std::endl;
    else
    {
         if (root && root->node.val == value)
         {
             Linklist *t = root;
             root = t->node.next;
             delete t;
             _size--;
         }
     }
     prev = root;
     active = root->node.next;
     while (active)
     {
         if (active->node.val == value)
         {
             prev->node.next = active->node.next;
             delete active;
             _size--;
             active = prev->node.next;
         }
         else
        {
            prev = active;
             active = active->node.next;
         }
     }
 }

 template<class T>
 void Linklist<T>::clear()
 {
     Linklist *t = root;
     while (t)
     {
         t = root->node.next;
         delete root;
         root = t;
     }
     root = NULL;
     tail = NULL;
     _size = 0;
 }

 template<class T>
 T Linklist<T>::at(int index)
 {
    Linklist *t = root;
     if (index < _size)
     {
         for (int i = 0; i < _size; i++)
         {
             t = t->node.next;
         }
     }
     else
     {
         t = NULL;
     }
     return (t);
 }

 template<class T>
 int Linklist<T>::size()
 {
     return (_size);
 }

这些似乎还可以。问题是当我试图在提供并修改的工厂类中创建一个Linklist对象时。

 #include "Factory.h"
 #include "Linklist.h"

 //You may add #include statements here
 /*
     You will MODIFY THIS DOCUMENT.
 */
 /*
     getLinkedListInt() and
     Creates and returns an object whose class extends LinkedListInterface.
     This should be an object of a class you have created.
     Example: If you made a class called "LinkedList", you might say, "return new      LinkedList<int>();".
 */
 LinkedListInterface<int> * Factory::getLinkedListInt()
 {
     return new Linklist<int>();
 }

 /*
     getLinkedListString() and
     Creates and returns an object whose class extends LinkedListInterface.
     This should be an object of a class you have created.
     Example: If you made a class called "LinkedList", you might say, "return new LinkedList<string>();".
 */
 LinkedListInterface<string>* Factory::getLinkedListString()
 {
     return new Linklist<string>();
 }

有人告诉我：

 undefined reference to `Linklist<int>::Linklist()'
 undefined reference to `Linklist<string>::Linklist()'

当我编译的时候。我不太了解模板，不知道我搞砸了什么。

有人有什么建议吗？

感谢