一种用于双向链表C++的插入方法

#include <iostream>

// 定义双向链表节点结构
struct Node {
    int data;
    Node* prev;
    Node* next;
    Node(int val) : data(val), prev(nullptr), next(nullptr) {}
};

// 定义双向链表类
class DoublyLinkedList {
public:
    DoublyLinkedList() : head(nullptr), tail(nullptr) {}

    // 头插法
    void insertAtHead(int value) {
        Node* newNode = new Node(value);
        if (!head) {
            head = tail = newNode;
        } else {
            newNode->next = head;
            head->prev = newNode;
            head = newNode;
        }
    }

    // 尾插法
    void insertAtTail(int value) {
        Node* newNode = new Node(value);
        if (!tail) {
            head = tail = newNode;
        } else {
            newNode->prev = tail;
            tail->next = newNode;
            tail = newNode;
        }
    }

    // 中间插法
    void insertAtPosition(int value, int position) {
        if (position <= 0) {
            insertAtHead(value);
            return;
        }

        Node* newNode = new Node(value);
        Node* current = head;
        int count = 0;

        while (current && count < position - 1) {
            current = current->next;
            count++;
        }

        if (!current) {
            insertAtTail(value);
        } else {
            newNode->next = current->next;
            newNode->prev = current;
            if (current->next) {
                current->next->prev = newNode;
            } else {
                tail = newNode;
            }
            current->next = newNode;
        }
    }

    // 打印链表
    void printList() {
        Node* current = head;
        while (current) {
            std::cout << current->data << " ";
            current = current->next;
        }
        std::cout << std::endl;
    }

private:
    Node* head;
    Node* tail;
};

int main() {
    DoublyLinkedList list;
    list.insertAtHead(1);
    list.insertAtTail(3);
    list.insertAtPosition(2, 2);
    list.printList(); // 输出: 1 2 3
    return 0;
}