用C语言来写单向链表的插入与删除操作

在C语言中，我们可以使用结构体（struct）和指针来创建和操作单向链表。以下是基本的插入和删除操作：

### 单向链表节点定义

typedef struct Node {
    int data;        // 数据域
    struct Node* next; // 指向下一个节点的指针
} Node;

#### 插入操作
- **在头部插入**：

void insertAtBeginning(Node** head, int value) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = value;
    newNode->next = *head;
    *head = newNode;
}

- **在尾部插入**：

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

- **在指定位置插入**：

void insertAfter(Node** head, int key, int value) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = value;
    Node* current = *head;
    while (current && current->data != key) {
        current = current->next;
    }
    if (current) {
        newNode->next = current->next;
        current->next = newNode;
    } else {
        printf("Element not found\n");
    }
}

#### 删除操作
- **删除头部元素**：

void deleteFirst(Node** head) {
    if (*head == NULL)
        return;
    Node* temp = *head;
    *head = (*head)->next;
    free(temp);
}

- **删除特定值的元素**：

void deleteNode(Node** head, int value) {
    if (*head == NULL)
        return;
    if ((*head)->data == value) {
        Node* temp = *head;
        *head = (*head)->next;
        free(temp);
        return;
    }
    Node* current = *head;
    while (current->next != NULL && current->next->data != value) {
        current = current->next;
    }
    if (current->next != NULL) {
        Node* toBeDeleted = current->next;
        current->next = current->next->next;
        free(toBeDeleted);
    }
}