用c++写一个双向链表

好的，我可以回答这个问题。以下是一个用 C 语言实现的双向链表的代码示例：

#include <stdio.h>
#include <stdlib.h>

struct Node {
    int data;
    struct Node* prev;
    struct Node* next;
};

struct Node* head = NULL;

void insertAtBeginning(int data) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = data;
    newNode->prev = NULL;
    newNode->next = head;
    if (head != NULL) {
        head->prev = newNode;
    }
    head = newNode;
}

void insertAtEnd(int data) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = data;
    newNode->next = NULL;
    if (head == NULL) {
        newNode->prev = NULL;
        head = newNode;
        return;
    }
    struct Node* lastNode = head;
    while (lastNode->next != NULL) {
        lastNode = lastNode->next;
    }
    lastNode->next = newNode;
    newNode->prev = lastNode;
}

void printList() {
    struct Node* currentNode = head;
    printf("List: ");
    while (currentNode != NULL) {
        printf("%d ", currentNode->data);
        currentNode = currentNode->next;
    }
    printf("\n");
}

int main() {
    insertAtEnd(1);
    insertAtBeginning(2);
    insertAtEnd(3);
    insertAtBeginning(4);
    printList();
    return 0;
}

这个程序实现了双向链表的插入和打印功能。在 `main` 函数中，我们先在链表末尾插入了一个元素 1，然后在链表开头插入了元素 2，再在末尾插入了元素 3，最后在开头插入了元素 4。最终打印出链表的内容为：4 2 1 3。