老铁们 以C结构体或C++的“类”代替“第2章中复杂数据类型”，实现“链式线性表”，编写下面6个接口函数：CreateList、ListPrint、GetElem、ListLength、ListInsert、ListDelete

1. 创建链表 CreateList：

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

Node* CreateList() {
    Node* head = (Node*)malloc(sizeof(Node));
    head->next = NULL;
    return head;
}

2. 打印链表 ListPrint：

void ListPrint(Node* head) {
    Node* p = head->next;
    while (p != NULL) {
        printf("%d ", p->data);
        p = p->next;
    }
    printf("\n");
}

3. 获取元素 GetElem：

int GetElem(Node* head, int index) {
    Node* p = head->next;
    int i = 0;
    while (p != NULL && i < index) {
        p = p->next;
        i++;
    }
    if (p == NULL || i > index) {
        printf("Error: Index out of range.\n");
        return -1;
    }
    else {
        return p->data;
    }
}

4. 获取链表长度 ListLength：

int ListLength(Node* head) {
    Node* p = head->next;
    int length = 0;
    while (p != NULL) {
        length++;
        p = p->next;
    }
    return length;
}

5. 插入元素 ListInsert：

void ListInsert(Node* head, int index, int value) {
    Node* p = head;
    int i = 0;
    while (p != NULL && i < index) {
        p = p->next;
        i++;
    }
    if (p == NULL || i > index) {
        printf("Error: Index out of range.\n");
    }
    else {
        Node* new_node = (Node*)malloc(sizeof(Node));
        new_node->data = value;
        new_node->next = p->next;
        p->next = new_node;
    }
}

6. 删除元素 ListDelete：

void ListDelete(Node* head, int index) {
    Node* p = head;
    int i = 0;
    while (p->next != NULL && i < index) {
        p = p->next;
        i++;
    }
    if (p->next == NULL || i > index) {
        printf("Error: Index out of range.\n");
    }
    else {
        Node* q = p->next;
        p->next = q->next;
        free(q);
    }
}