C++ 手动实现双向链表（作业版）

双向链表，并实现增删查改等功能

首先定义节点类，类成员包含当前节点的值， 指向下一个节点的指针和指向上一个节点的指针

//节点定义
template <typename T>
class Node {
public:
    Node<T>* prior;
    T value;
    Node<T>* next;
    Node():value(0),prior(nullptr),next(nullptr) {}
    Node(T n):prior(nullptr),value(n),next(nullptr) {}
};

然后是链表类的定义，主要包含了增删查改等功能

//双向链表定义
template <typename T>
class LinkList_doubly {
public:
    Node<T>* firstNode;
    Node<T>* lastNode;

    LinkList_doubly();
    LinkList_doubly(int n, const T* arr);
    LinkList_doubly(const LinkList_doubly<T>& link);
    ~LinkList_doubly();
    LinkList_doubly<T>& push_back(T n);
    LinkList_doubly<T>& push_front(T n);
    LinkList_doubly<T>& insert(int pos, int n, T* arr);
    LinkList_doubly<T>& pop_front();
    LinkList_doubly<T>& pop_back();
    LinkList_doubly<T>& remove(int pos, int num);
    LinkList_doubly<T>& reverse();
    T& operator[](int n);
    T& at(int n);
    LinkList_doubly<T>& replace(int pos, int n, T* arr);
    int getLen() {return len;}
    void clear() {this->~LinkList_doubly();}
    void display();
private:
    int len = 0;
    Node<T>* getNode_next(int n);

};

各个函数解释：

LinkList_doubly();      默认构造函数

LinkList_doubly(const T* arr, int len);      一般构造函数

LinkList_doubly(const LinkList<T>& link)           拷贝构造函数

~LinkList_doubly();     析构函数

LinkList_doubly<T>& push_back(T n);    在尾部添加一个元素

LinkList_doubly<T>& push_front(T n);     在头部添加一个元素

LinkList_doubly<T>& insert(int pos, int n, T* arr);   在pos处插入n个元素

LinkList_doubly<T>& pop_front();    删除第一个节点

LinkList_doubly<T>& pop_back();    删除最后一个节点

LinkList_doubly<T>& remove(int pos, int num);     删除pos开始的num个元素

LinkList_doubly<T>& reverse();     反转链表

T& operator[](int n);     重载[ ]运算符，返回第n个节点的值

T& at(int n);                 与[ ]一样，只不过会检查索引是否越界

LinkList_doubly<T>& replace(int pos, int n, T* arr);    替换n个节点

int getLen() {return len;}     返回长度，因为len是private

void clear() {this->~LinkList();}    清除链表

void display();    显示链表所有元素

Node<T>* getNode_next(int n);     返回第n个节点的next指针

#include <iostream>
using namespace std;

template <typename T>
class Node {
public:
    Node<T>* prior;
    T value;
    Node<T>* next;
    Node():value(0),prior(nullptr),next(nullptr) {}
    Node(T n):prior(nullptr),value(n),next(nullptr) {}
};

template <typename T>
class LinkList_doubly {
public:
    Node<T>* firstNode;
    Node<T>* lastNode;

    LinkList_doubly();
    LinkList_doubly(int n, const T* arr);
    LinkList_doubly(const LinkList_doubly<T>& link);
    ~LinkList_doubly();
    LinkList_doubly<T>& push_back(T n);
    LinkList_doubly<T>& push_front(T n);
    LinkList_doubly<T>& insert(int pos, int n, T* arr);
    LinkList_doubly<T>& pop_front();
    LinkList_doubly<T>& pop_back();
    LinkList_doubly<T>& remove(int pos, int num);
    LinkList_doubly<T>& reverse();
    T& operator[](int n);
    T& at(int n);
    LinkList_doubly<T>& replace(int pos, int n, T* arr);
    int getLen() {return len;}
    void clear() {this->~LinkList_doubly();}
    void display();
private:
    int len = 0;
    Node<T>* getNode_next(int n);

};

//默认构造函数
template <typename T>
LinkList_doubly<T>::LinkList_doubly() {
    firstNode = nullptr;
    lastNode = nullptr;
    len = 0;
}

//一般构造函数，用数组进行初始化
template <typename T>
LinkList_doubly<T>::LinkList_doubly(int n, const T* arr) {
    Node<T>* temp1 = nullptr;
    Node<T>* temp2 = nullptr;
    for (int i = 0; i < n; i++) {
        temp1 = new Node<T> (arr[i]);
        if ( i == 0 )
            firstNode = temp1;
        if ( i == n-1 )
            lastNode = temp1;
        temp1->prior = temp2;
        if ( i > 0 )
            temp2->next  = temp1;
        temp2 = temp1;
    }
    this->len = n;
}

//拷贝构造函数
template <typename T>
LinkList_doubly<T>::LinkList_doubly(const LinkList_doubly<T>& link) {
    this->firstNode = link.firstNode;
    this->lastNode  = link.lastNode;
    this->len = link.getLen();
}

//析构函数
template <typename T>
LinkList_doubly<T>::~LinkList_doubly() {
    this->len = 0;
    Node<T>* temp = firstNode;
    lastNode = nullptr;
    while ( firstNode ) {
        temp = firstNode;
        firstNode = firstNode->next;
        delete temp;
        temp = nullptr;
    }
}

//在尾部添加一个元素
template <typename T>
LinkList_doubly<T>& LinkList_doubly<T>::push_back(T n) {
    Node<T>* newNode = new Node<T> (n);
    newNode->prior = lastNode;
    lastNode->next = newNode;
    lastNode = newNode;
    len++;
    return *this;
}

//在头部添加一个元素
template <typename T>
LinkList_doubly<T>& LinkList_doubly<T>::push_front(T n) {
    Node<T>* newNode = new Node<T> (n);
    newNode->next = firstNode;
    firstNode->prior = newNode;
    firstNode = newNode;
    len++;
    return *this;
}

//在position位置插入n个元素
template <typename T>
LinkList_doubly<T>& LinkList_doubly<T>::insert(int pos, int n, T* arr) {
    if ( pos < 0 || pos > len-1 ) {
        cout << "[error]: illegal insert index, please check" << endl;
        exit(0);
    }
    if ( pos == 0 ) {
        for ( int i = 0; i < n; i++ )
            this->push_front(arr[n-1-i]);  //push_front自带len++
        return *this;
    }
    Node<T>* temp_end = getNode_next(pos);
    Node<T>* temp_front = getNode_next(pos-1);
    Node<T>* temp_new = nullptr;
    for ( int i = 0; i < n; i++ ) {
        temp_new = new Node<T> (arr[i]);
        temp_front->next = temp_new;
        temp_new->prior = temp_front;
        temp_front = temp_front->next;
    }
    temp_front->next = temp_end;
    temp_end->prior = temp_front;
    len += n;
    return *this;
}

//删除第一个元素
template <typename T>
LinkList_doubly<T>& LinkList_doubly<T>::pop_front() {
    if ( len == 0 ) {
        cout << "[warning]: linkedlist is empty" << endl;
        return *this;
    }
    Node<T>* temp = firstNode;
    firstNode = firstNode->next;
    firstNode->prior = nullptr;
    delete temp;
    len--;
    return *this;
}

//删除最后一个元素
template <typename T>
LinkList_doubly<T>& LinkList_doubly<T>::pop_back() {
    if ( len == 0 ) {
        cout << "[warning]: linkedlist is empty" << endl;
        return *this;
    }
    Node<T>* temp = lastNode;
    lastNode = lastNode->prior;
    lastNode->next = nullptr;
    delete temp;
    len--;
    return *this;
}

//删除position开始的num个元素
template <typename T>
LinkList_doubly<T>& LinkList_doubly<T>::remove(int pos, int num) {
    if ( pos > len-1 || len < 0 || pos < 0 || pos > len-1) {
        cout << "[error]: illegal remove position, please check again" << endl;
        exit(0);
    } else if ( pos + num - 1 > len-1) {
        cout << "[error]: remove index out of range" << endl;
        exit(0);
    }
    //如果删除了首元节点或者尾节点，要考虑firstNode和lastNode的指向，用pop比较方便
    if ( pos == 0 ) {
        for ( int i = 0; i < num; i++ )
            this->pop_front();
        return *this;
    }
    if ( pos + num == len ) {
        for ( int i = 0; i < num; i++ )
            this->pop_back();
        return *this;
    }
    Node<T>* temp_front = getNode_next(pos-1);
    Node<T>* temp_end = getNode_next(pos+num);
    Node<T>* temp = getNode_next(pos);
    while ( 1 ) {
        Node<T>* node = temp;
        temp = temp->next;
        delete node;
        if ( temp == temp_end ) {
            break;
        }
    }
    temp_front->next = temp_end;
    temp_end->prior = temp_front;
    len -= num;
    return *this;
}

//替换元素
template <typename T>
LinkList_doubly<T>& LinkList_doubly<T>::replace(int pos, int n, T* arr) {
    Node<T>* temp = getNode_next(pos);
    for ( int i = 0; i < n; i++ ) {
        temp->value = arr[i];
        temp = temp->next;
    }
    return *this;
}

//反转链表,终极偷懒写法，实在不想动脑子了
template <typename T>
LinkList_doubly<T>& LinkList_doubly<T>::reverse() {
    const int num = len;
    T arr[num];
    Node<T>* temp = firstNode;
    for ( int i = 0; i < this->len; i++ ) {
        arr[i] = temp->value;
        temp = temp->next;
    }
    temp = lastNode;
    for ( int i = 0; i < this->len; i++ ) {
        temp->value = arr[i];
        temp = temp->prior;
    }
    return *this;
}

//访问第n个元素
template <typename T>
T& LinkList_doubly<T>::operator[](int n){
    Node<T>* temp = nullptr;
    if ( n <= len/2 ) {
        temp = firstNode;
        for ( int i = 0; i < n; i++ ) {
            temp = temp->next;
        }
    } else {
        temp = lastNode;
        for ( int i = 0; i < len-1-n; i++ ) {
            temp = temp->prior;
        }
    }
    return temp->value;

}

//访问第n个元素,增加索引检查

template <typename T>
T& LinkList_doubly<T>::at(int n){
    if ( n < 0 || n > len-1 ) {
        cout << "[error]:index out of range" << endl;
        exit(0);
    }
    return (*this)[n];
}
//获取第n个Node的next指针
template <typename T>
Node<T>* LinkList_doubly<T>::getNode_next(int n) {
    if ( n > len-1 ) {
        cout << "[error]: illegal index" << endl;
    }
    Node<T>* temp = firstNode;
    for ( int i = 0; i < n; i++ ) {
        temp = temp->next;
    }
    return temp;
}

//显示链表所有元素，会对链表正反向一致性进行检查
template <typename T>
void LinkList_doubly<T>::display() {
    const int num = len;
    T arr1[num];
    T arr2[num];
    Node<T>* temp = firstNode;
    for ( int i = 0; i < this->len; i++ ) {
        arr1[i] = temp->value;
        temp = temp->next;
    }
    temp = lastNode;
    for ( int i = 0; i < this->len; i++ ) {
        arr2[i] = temp->value;
        temp = temp->prior;
    }
    for ( int i = 0; i < this->len; i++ ) {
        if ( arr1[i] != arr2[len-1-i] ) {
            cout << "第"<<i<<"个元素正反向结果不一致" <<  arr1[i] << " " << arr2[len-1-i] << endl;
            exit(0);
        }
    }

    temp = firstNode;
    for ( int i = 0; i < this->len; i++ ) {
        cout << temp->value << " ";
        temp = temp->next;
    }
    cout << endl;
}

int main() {
    int arr[] = {1,5,7,3,5,3,1};
    LinkList_doubly<int> link(sizeof(arr)/sizeof(int), arr);
    link.display();
    link.push_back(25);
    link.display();
    link.push_front(10);
    link.display();
    int arr2[] = {1,0,0,4};
    link.insert(0,sizeof(arr2)/sizeof(int), arr2);
    link.display();
    link.pop_front();
    link.display();
    link.pop_back();
    link.display();
    link.remove(7,2);
    link.display();
    int arr3[] = {2,3,5};
    link.replace(4, sizeof(arr3)/sizeof(int), arr3);
    link.display();
    link.reverse();
    link.display();
    cout << link[8] << " " << link.at(3) << endl;
    cout << link.getLen() << endl;
    link.~LinkList_doubly();
    cout << link.getLen() << endl;

}