C语言实现双向链表中插入结点并输出

以下是C语言实现双向链表中插入结点并输出的代码：

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

// 双向链表结构体
struct Node {
    int data;
    struct Node* prev;
    struct Node* next;
};

// 在链表头插入结点
struct Node* insertAtBeginning(struct Node* head, int newData) {
    // 创建新结点
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = newData;
    newNode->prev = NULL;
    newNode->next = head;

    // 如果链表不为空，修改头结点的prev指针
    if (head != NULL) {
        head->prev = newNode;
    }

    // 返回新的头结点
    return newNode;
}

// 在链表尾插入结点
struct Node* insertAtEnd(struct Node* head, int newData) {
    // 创建新结点
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = newData;
    newNode->next = NULL;

    // 如果链表为空，新结点即为头结点
    if (head == NULL) {
        newNode->prev = NULL;
        return newNode;
    }

    // 找到链表尾部结点并修改指针
    struct Node* curr = head;
    while (curr->next != NULL) {
        curr = curr->next;
    }
    curr->next = newNode;
    newNode->prev = curr;

    // 返回头结点
    return head;
}

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

int main() {
    struct Node* head = NULL;

    // 插入结点并输出链表
    head = insertAtEnd(head, 1);
    printList(head);
    head = insertAtEnd(head, 2);
    printList(head);
    head = insertAtBeginning(head, 3);
    printList(head);
    head = insertAtEnd(head, 4);
    printList(head);

    return 0;
}

输出结果：

List: 1 
List: 1 2 
List: 3 1 2 
List: 3 1 2 4