关于自定义单链表实现Student类型数据存放的问题，主要是结点的构造不太明白！(语言-c++)

Question

实验要求： main 函数中利用单向链表类 SingleLinkedList， 定义和初始化一个 Student 类型的线性链表，在表中添加（push_back）和插入（insert）新的元素。

结点的构造

template<typename T>
class SLNode
{
public:
    T _data;
    SLNode<T>* next; 
    
    SLNode()
    {
        this->_data = NULL;
        this-> next = NULL;
    }
};

链表的实现

template<typename T>
class SingleLinkedList
{
private:
    SLNode<T>* _head;
    int _count;

public:

    SingleLinkedList()
    {
        SLNode<T>* _head = NULL;
        this->_count = NULL;
    }

    void push_back(SingleLinkedList* L, T data)
    {
        SLNode<T>* new_node = new SLNode();
        new_node->_data = data;
        new_node->next = NULL;

        SLNode<T>* last_node = L->_head;
        for (int i = 0; i < _count; i++)
        {
            last_node = last_node->next;
        }
        new_node->next = last_node->next;
        last_node->next = new_node;
    }
    void insert(SingleLinkedList* L, int pos, T data)
    {
        if (L == NULL)
        {
            pos = 0;
        }
        SLNode<T>* new_node = new SLNode();
        new_node->_data = data;
        new_node->next = NULL;

        SLNode<T>* pos_node = L->_head;
        for (int i = 0; i < pos; i++)
            pos_node = pos_node->next;
        new_node->next = pos_node->next;
        pos_node->next = new_node;
        L->_count++;
    }

    void show(SingleLinkedList* L)
    {
        if (L->_count == 0)
            cout << "该链表中没有数据" << endl;
        else {
            SLNode<T>* pcurrent = L->_head->next;
            while (pcurrent != NULL)
            {
                cout << pcurrent->_data << endl;
                pcurrent = pcurrent->next;
            }
            cout << endl;
        }
    }

};

测试函数

int main()
{
    
    Student s1 = { 001,"桑桑",18.0f,88.0l };
    Student s2 = { 002,"稚稚",8.0f,77.0l };
    Student s3 = { 000,"渊渊",25.0f,99.0l };
    SingleLinkedList<Student> L1;
        cout << s1 << endl;
    L1.push_back(&L1,s1);
    L1.push_back(&L1,s2);
    cout << s1 << endl;
    L1.insert(&L1, 0, s3);
    L1.show(&L1);
}

Student类

class Student
{
public:
    Student(int id, string name, float age, double score);
    ~Student();
    friend ostream& operator<<(ostream&os, const Student&s)
    {
       os << "学号:" << s._id << "  姓名：" << s._name << "  年龄" << s._age << "  成绩：" << s._score << endl;
            return os;
        
    }
    string str()
    {
        cout << "内部输出:" << endl;
        cout << "学号:" << _id << "  姓名：" << _name << "  年龄" << _age << "  成绩：" << _score << endl;
        return "\n";
    };
    Student& operator =(const Student&x)
    {
        this->_id = x._id;
        this->_age = x._age;
        this->_score = x._score;
        this->_name = x._name;
        
    
    }
private:
    int _id;
    string _name;
    float _age;
    double _score;

};

Student::Student(int id, string name, float age, double score)
{
    _id = id;
    _name = name;
    _age = age;
    _score = score;
}

Student::~Student()
{
}

报错

已启动生成…
1>------ 已启动生成: 项目: ex4p4, 配置: Debug x64 ------
1>p4.cpp
1>C:\Users\86150\source\repos\ex3\dsa\SingledLinkedList.h(83,1): error C2514: “SLNode”: 无法构建类模板
1>C:\Users\86150\source\repos\ex3\dsa\SingledLinkedList.h(7): message : 参见“SLNode”的声明
1>C:\Users\86150\source\repos\ex3\dsa\SingledLinkedList.h(83): message : 查看对正在编译的 类 模板 实例化“SingleLinkedList<T>”的引用
1>已完成生成项目“ex4p4.vcxproj”的操作 - 失败。
========== 生成: 成功 0 个，失败 1 个，最新 1 个，跳过 0 个 ==========

错误    C2514    “SLNode”: 无法构建类模板    ex4p4    C:\Users\86150\source\repos\ex3\dsa\SingledLinkedList.h    83    //83是最后一行，有点迷惑

希望可以详细指出我的错误原因，以及如何改正

Answer 1

代码修改如下：

#include <iostream>
using namespace std;

template<typename T>
class SingleLinkedList
{
private:
    class SLNode
    {
    public:
        T _data;
        SLNode* next;

        SLNode()
        {
            //this->_data = 0;
            this->next = NULL;
        }
    };
    SLNode* _head;
    int _count;

public:

    SingleLinkedList()
    {
        _head =  new SLNode();
        _head->next = NULL;
        //SLNode<T>* _head = NULL;
        this->_count = 0;
    }

    void push_back( T data)
    {
        SLNode* new_node = new SLNode();
        new_node->_data = data;
        new_node->next = NULL;

        SLNode* last_node = _head;
        for (int i = 0; i < _count; i++)
        {
            last_node = last_node->next;
        }
        new_node->next = last_node->next;
        last_node->next = new_node;
    }
    void insert(int pos, T data)
    {
        if (_head == NULL)
        {
            pos = 0;
        }
        SLNode* new_node = new SLNode();
        new_node->_data = data;
        new_node->next = NULL;

        SLNode* pos_node = _head;
        for (int i = 0; i < pos; i++)
            pos_node = pos_node->next;
        new_node->next = pos_node->next;
        pos_node->next = new_node;
        _count++;
    }

    void show()
    {
        if (_count == 0)
            cout << "该链表中没有数据" << endl;
        else {
            SLNode* pcurrent = _head->next;
            while (pcurrent != NULL)
            {
                cout << pcurrent->_data << endl;
                pcurrent = pcurrent->next;
            }
            cout << endl;
        }
    }

};

class Student
{
public:
    Student();
    Student(int id, string name, float age, double score);
    ~Student();
    friend ostream& operator<<(ostream& os, const Student& s)
    {
        os << "学号:" << s._id << "  姓名：" << s._name << "  年龄" << s._age << "  成绩：" << s._score << endl;
        return os;

    }
    string str()
    {
        cout << "内部输出:" << endl;
        cout << "学号:" << _id << "  姓名：" << _name << "  年龄" << _age << "  成绩：" << _score << endl;
        return "\n";
    };
    Student& operator =(const Student& x)
    {
        this->_id = x._id;
        this->_age = x._age;
        this->_score = x._score;
        this->_name = x._name;
        return *this;

    }
private:
    int _id;
    string _name;
    float _age;
    double _score;

};
Student::Student()
{
    _id = 0;
    _name = "";
    _age = 0;
    _score = 0;
}
Student::Student(int id, string name, float age, double score)
{
    _id = id;
    _name = name;
    _age = age;
    _score = score;
}

Student::~Student()
{
}





int main()
{

    Student s1 = { 001,"桑桑",18.0f,88.0l };
    Student s2 = { 002,"稚稚",8.0f,77.0l };
    Student s3 = { 000,"渊渊",25.0f,99.0l };
    SingleLinkedList<Student> L1;
    cout << s1 << endl;
    L1.push_back(s1);
    L1.push_back(s2);
    cout << s1 << endl;
    L1.insert(0, s3);
    L1.show();
    return 0;
}