使用c语言实现单链表，包括初始化单链表、判断单链表是否为空、获取单链表长度、 在单链表末尾插入节点、在单链表指定位置插入节点、删除单链表指定位置的节点、 获取单链表指定位置的节点值、修改单链表指定位置的节点值、输出单链表等操作。并在主函数中进行测试

好的，我会为您介绍如何使用 C 语言实现单链表。首先，我们需要定义一个结构体来表示每个节点：

typedef struct Node {
    int data;           // 数据域
    struct Node* next;  // 指针域
} Node;

接下来，我们需要实现单链表的各种操作：

1. 初始化单链表

void initList(Node** head) {
    *head = NULL;
}

2. 判断单链表是否为空

int isEmpty(Node* head) {
    return head == NULL;
}

3. 获取单链表长度

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

4. 在单链表末尾插入节点

void insertAtEnd(Node** head, int data) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = data;
    newNode->next = NULL;
    if (*head == NULL) {
        *head = newNode;
    } else {
        Node* p = *head;
        while (p->next != NULL) {
            p = p->next;
        }
        p->next = newNode;
    }
}

5. 在单链表指定位置插入节点

void insertAtPos(Node** head, int pos, int data) {
    if (pos < 1 || pos > getLength(*head) + 1) {
        printf("Invalid position!\n");
        return;
    }
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = data;
    if (pos == 1) {
        newNode->next = *head;
        *head = newNode;
    } else {
        Node* p = *head;
        for (int i = 1; i < pos - 1; i++) {
            p = p->next;
        }
        newNode->next = p->next;
        p->next = newNode;
    }
}

6. 删除单链表指定位置的节点

void deleteAtPos(Node** head, int pos) {
    if (pos < 1 || pos > getLength(*head)) {
        printf("Invalid position!\n");
        return;
    }
    if (pos == 1) {
        Node* p = *head;
        *head = (*head)->next;
        free(p);
    } else {
        Node* p = *head;
        for (int i = 1; i < pos - 1; i++) {
            p = p->next;
        }
        Node* q = p->next;
        p->next = q->next;
        free(q);
    }
}

7. 获取单链表指定位置的节点值

int getValueAtPos(Node* head, int pos) {
    if (pos < 1 || pos > getLength(head)) {
        printf("Invalid position!\n");
        return -1;
    }
    Node* p = head;
    for (int i = 1; i < pos; i++) {
        p = p->next;
    }
    return p->data;
}

8. 修改单链表指定位置的节点值

void setValueAtPos(Node* head, int pos, int data) {
    if (pos < 1 || pos > getLength(head)) {
        printf("Invalid position!\n");
        return;
    }
    Node* p = head;
    for (int i = 1; i < pos; i++) {
        p = p->next;
    }
    p->data = data;
}

9. 输出单链表

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

最后，在主函数中进行测试：

int main() {
    Node* head;
    initList(&head);
    printf("Length: %d\n", getLength(head));
    insertAtEnd(&head, 1);
    insertAtEnd(&head, 2);
    insertAtEnd(&head, 3);
    printf("Length: %d\n", getLength(head));
    printList(head);
    insertAtPos(&head, 2, 4);
    printf("Length: %d\n", getLength(head));
    printList(head);
    deleteAtPos(&head, 3);
    printf("Length: %d\n", getLength(head));
    printList(head);
    printf("Value at position 2: %d\n", getValueAtPos(head, 2));
    setValueAtPos(head, 2, 5);
    printf("Value at position 2: %d\n", getValueAtPos(head, 2));
    printList(head);
    return 0;
}

输出结果为：

Length: 0
Length: 3
1 2 3 
Length: 4
1 4 2 3 
Length: 3
1 4 3 
Value at position 2: 4
Value at position 2: 5
1 5 3