怎样用c语言查看双链表的长度

要查看双链表的长度，需要遍历整个链表并计算节点数。下面是一个示例代码，使用了一个计数器变量来统计节点数：

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

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

int getLength(struct Node* head) {
    int count = 0;
    struct Node* current = head;
    while (current != NULL) {
        count++;
        current = current->next;
    }
    return count;
}

int main() {
    // 创建一个双链表
    struct Node* head = NULL;
    struct Node* second = NULL;
    struct Node* third = NULL;

    head = (struct Node*)malloc(sizeof(struct Node));
    second = (struct Node*)malloc(sizeof(struct Node));
    third = (struct Node*)malloc(sizeof(struct Node));

    head->data = 1;
    head->prev = NULL;
    head->next = second;

    second->data = 2;
    second->prev = head;
    second->next = third;

    third->data = 3;
    third->prev = second;
    third->next = NULL;

    // 获取链表长度并输出
    int length = getLength(head);
    printf("Length of the linked list is: %d\n", length);

    // 释放内存
    free(head);
    free(second);
    free(third);

    return 0;
}

以上代码创建了一个包含三个节点的双链表，并使用 `getLength()` 函数来获取链表的长度，并输出结果。