从函数写入链表时，链表状态不变

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

// 定义链表节点结构体
struct Node {
    int data;
    struct Node* next;
};

// 创建新节点
struct Node* createNode(int data) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = data;
    newNode->next = NULL;
    return newNode;
}

// 在链表末尾添加节点
void appendNode(struct Node** head, int data) {
    struct Node* newNode = createNode(data);
    if (*head == NULL) {
        *head = newNode;
        return;
    }
    struct Node* temp = *head;
    while (temp->next != NULL) {
        temp = temp->next;
    }
    temp->next = newNode;
}

// 打印链表
void printList(struct Node* head) {
    struct Node* temp = head;
    while (temp != NULL) {
        printf("%d -> ", temp->data);
        temp = temp->next;
    }
    printf("NULL\n");
}

// 修改链表的函数
void modifyList(struct Node** head, int index, int newData) {
    struct Node* temp = *head;
    int count = 0;
    while (temp != NULL && count < index) {
        temp = temp->next;
        count++;
    }
    if (temp != NULL) {
        temp->data = newData;
    }
}

int main() {
    struct Node* head = NULL;
    appendNode(&head, 1);
    appendNode(&head, 2);
    appendNode(&head, 3);

    printf("Original List: ");
    printList(head);

    modifyList(&head, 1, 10);

    printf("Modified List: ");
    printList(head);

    return 0;
}