、使用系统文件IO实现链表的读写操作 要求： 封装4个函数，分别是创建链表，遍历链表， 写链表，读链表 先写一个程序创建链表，然后写入文件 然后再写一个程序读链表，遍历链表用

首先，我们需要定义一个链表节点结构体，然后实现创建链表、遍历链表、写链表和读链表的函数。以下是一个简单的示例：

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

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

// 创建链表
Node *create_list(int n) {
    Node *head = NULL, *tail = NULL;
    for (int i = 0; i < n; i++) {
        Node *new_node = (Node *)malloc(sizeof(Node));
        new_node->data = i + 1;
        new_node->next = NULL;
        if (head == NULL) {
            head = new_node;
            tail = new_node;
        } else {
            tail->next = new_node;
            tail = new_node;
        }
    }
    return head;
}

// 遍历链表
void traverse_list(Node *head) {
    Node *current = head;
    while (current != NULL) {
        printf("%d ", current->data);
        current = current->next;
    }
    printf("
");
}

// 写链表到文件
void write_list_to_file(Node *head, const char *filename) {
    FILE *file = fopen(filename, "w");
    if (file == NULL) {
        printf("无法打开文件
");
        return;
    }
    Node *current = head;
    while (current != NULL) {
        fprintf(file, "%d ", current->data);
        current = current->next;
    }
    fclose(file);
}

// 从文件中读取链表
Node *read_list_from_file(const char *filename) {
    FILE *file = fopen(filename, "r");
    if (file == NULL) {
        printf("无法打开文件
");
        return NULL;
    }
    Node *head = NULL, *tail = NULL;
    int data;
    while (fscanf(file, "%d", &data) == 1) {
        Node *new_node = (Node *)malloc(sizeof(Node));
        new_node->data = data;
        new_node->next = NULL;
        if (head == NULL) {
            head = new_node;
            tail = new_node;
        } else {
            tail->next = new_node;
            tail = new_node;
        }
    }
    fclose(file);
    return head;
}

int main() {
    int n = 5;
    Node *head = create_list(n);
    traverse_list(head);
    write_list_to_file(head, "list.txt");
    Node *read_head = read_list_from_file("list.txt");
    traverse_list(read_head);
    return 0;
}

这个程序首先创建一个包含5个节点的链表，然后将其写入名为"list.txt"的文件。接着，它从该文件中读取链表并遍历打印出来。