用c++代码实现常见的链表操作，插入头部，尾部，某数据之后或之前，修改，删除，排序，存储到文件，从文件构建链表，判空，是否存在，清空，排序

以下是用C语言实现常见链表操作的示例代码：

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

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

// 插入头部
void insertAtHead(Node **head, int data) {
    Node *newNode = (Node*) malloc(sizeof(Node));
    newNode->data = data;
    newNode->next = *head;
    *head = newNode;
}

// 插入尾部
void insertAtTail(Node **head, int data) {
    Node *newNode = (Node*) malloc(sizeof(Node));
    newNode->data = data;
    newNode->next = NULL;
    if (*head == NULL) {
        *head = newNode;
    } else {
        Node *temp = *head;
        while (temp->next != NULL) {
            temp = temp->next;
        }
        temp->next = newNode;
    }
}

// 插入某数据之后
void insertAfter(Node *node, int data) {
    if (node == NULL) {
        return;
    }
    Node *newNode = (Node*) malloc(sizeof(Node));
    newNode->data = data;
    newNode->next = node->next;
    node->next = newNode;
}

// 插入某数据之前
void insertBefore(Node **head, Node *node, int data) {
    if (node == NULL) {
        return;
    }
    if (*head == node) {
        insertAtHead(head, data);
        return;
    }
    Node *newNode = (Node*) malloc(sizeof(Node));
    newNode->data = data;
    Node *temp = *head;
    while (temp->next != node) {
        temp = temp->next;
    }
    newNode->next = node;
    temp->next = newNode;
}

// 修改节点
void modifyNode(Node *node, int data) {
    if (node == NULL) {
        return;
    }
    node->data = data;
}

// 删除节点
void deleteNode(Node **head, Node *node) {
    if (*head == NULL || node == NULL) {
        return;
    }
    if (*head == node) {
        *head = node->next;
        free(node);
        return;
    }
    Node *temp = *head;
    while (temp->next != node) {
        temp = temp->next;
    }
    temp->next = node->next;
    free(node);
}

// 排序链表
void sortList(Node **head) {
    if (*head == NULL || (*head)->next == NULL) {
        return;
    }
    Node *curr, *prev, *next;
    int swapped;
    do {
        swapped = 0;
        curr = *head;
        prev = NULL;
        while (curr->next != NULL) {
            next = curr->next;
            if (curr->data > next->data) {
                swapped = 1;
                curr->next = next->next;
                next->next = curr;
                if (prev == NULL) {
                    *head = next;
                } else {
                    prev->next = next;
                }
                prev = next;
            } else {
                prev = curr;
                curr = curr->next;
            }
        }
    } while (swapped);
}

// 存储链表到文件
void saveListToFile(Node *head, char *filename) {
    FILE *fp = fopen(filename, "w");
    if (fp == NULL) {
        printf("Error opening file.\n");
        return;
    }
    Node *temp = head;
    while (temp != NULL) {
        fprintf(fp, "%d ", temp->data);
        temp = temp->next;
    }
    fclose(fp);
}

// 从文件构建链表
void buildListFromFile(Node **head, char *filename) {
    FILE *fp = fopen(filename, "r");
    if (fp == NULL) {
        printf("Error opening file.\n");
        return;
    }
    int data;
    while (fscanf(fp, "%d", &data) != EOF) {
        insertAtTail(head, data);
    }
    fclose(fp);
}

// 判断链表是否为空
int isEmpty(Node *head) {
    return (head == NULL);
}

// 判断某数据是否存在于链表中
int contains(Node *head, int data) {
    Node *temp = head;
    while (temp != NULL) {
        if (temp->data == data) {
            return 1;
        }
        temp = temp->next;
    }
    return 0;
}

// 清空链表
void clearList(Node **head) {
    Node *temp;
    while (*head != NULL) {
        temp = *head;
        *head = (*head)->next;
        free(temp);
    }
}

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

int main() {
    Node *head = NULL;
    insertAtHead(&head, 4);
    insertAtHead(&head, 3);
    insertAtTail(&head, 5);
    insertAfter(head->next, 6);
    insertBefore(&head, head->next, 2);
    printList(head); // 输出 3 2 4 6 5
    modifyNode(head->next, 1);
    deleteNode(&head, head->next);
    sortList(&head);
    printList(head); // 输出 2 3 4 5
    saveListToFile(head, "list.txt");
    clearList(&head);
    buildListFromFile(&head, "list.txt");
    printf("Is list empty? %d\n", isEmpty(head));
    printf("Does list contain 4? %d\n", contains(head, 4));
    printList(head); // 输出 2 3 4 5
    clearList(&head);
    printf("Is list empty? %d\n", isEmpty(head));
    return 0;
}