C语言双向链表通讯录，支持保存数据到文件加载数据到文件

下面是一个简单的C语言双向链表实现通讯录，支持保存数据到文件和加载数据到文件的示例代码：

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

// 定义通讯录结构体
typedef struct _address_book {
    char name[20];  // 姓名
    char phone[20]; // 电话号码
    struct _address_book *prev; // 上一个节点的指针
    struct _address_book *next; // 下一个节点的指针
} address_book;

// 创建一个新的通讯录节点
address_book *new_address_book(char *name, char *phone) {
    // 分配内存
    address_book *node = (address_book *)malloc(sizeof(address_book));
    if (node == NULL) {
        printf("Error: memory allocation failed!\n");
        exit(1);
    }
    
    // 复制数据
    strncpy(node->name, name, 19);
    strncpy(node->phone, phone, 19);
    node->prev = NULL;
    node->next = NULL;
    
    return node;
}

// 添加一个通讯录节点到双向链表
void add_address_book(address_book **head, address_book *node) {
    if (*head == NULL) { // 如果链表为空则直接添加
        *head = node;
    } else { // 否则添加到链表末尾
        address_book *current = *head;
        while (current->next != NULL) {
            current = current->next;
        }
        current->next = node;
        node->prev = current;
    }
}

// 从双向链表中删除一个通讯录节点
void delete_address_book(address_book **head, char *name) {
    if (*head == NULL) { // 如果链表为空则直接返回
        return;
    }
    
    address_book *current = *head;
    while (current != NULL) {
        if (strcmp(current->name, name) == 0) { // 找到了要删除的节点
            if (current == *head) { // 要删除的节点是头节点
                *head = current->next;
                if (*head != NULL) {
                    (*head)->prev = NULL;
                }
            } else { // 要删除的节点不是头节点
                current->prev->next = current->next;
                if (current->next != NULL) {
                    current->next->prev = current->prev;
                }
            }
            free(current); // 释放内存
            return;
        }
        current = current->next;
    }
}

// 打印所有的通讯录节点
void print_address_book(address_book *head) {
    printf("Name\tPhone\n");
    printf("----\t-----\n");
    address_book *current = head;
    while (current != NULL) {
        printf("%s\t%s\n", current->name, current->phone);
        current = current->next;
    }
    printf("\n");
}

// 保存通讯录到文件
void save_address_book(address_book *head, char *filename) {
    FILE *fp = fopen(filename, "w");
    if (fp == NULL) {
        printf("Error: cannot open file %s for writing!\n", filename);
        exit(1);
    }
    
    address_book *current = head;
    while (current != NULL) {
        fprintf(fp, "%s,%s\n", current->name, current->phone);
        current = current->next;
    }
    
    fclose(fp);
}

// 从文件中加载通讯录
address_book *load_address_book(char *filename) {
    FILE *fp = fopen(filename, "r");
    if (fp == NULL) {
        printf("Error: cannot open file %s for reading!\n", filename);
        exit(1);
    }
    
    address_book *head = NULL;
    char line[50];
    char *name, *phone;
    while (fgets(line, 50, fp) != NULL) {
        // 解析行数据
        name = strtok(line, ",");
        phone = strtok(NULL, ",");
        if (name != NULL && phone != NULL) {
            // 创建新节点并添加到链表中
            address_book *node = new_address_book(name, phone);
            add_address_book(&head, node);
        }
    }
    
    fclose(fp);
    return head;
}

int main() {
    address_book *head = NULL;
    
    // 添加几个测试节点
    add_address_book(&head, new_address_book("Alice", "123456"));
    add_address_book(&head, new_address_book("Bob", "234567"));
    add_address_book(&head, new_address_book("Charlie", "345678"));
    
    // 打印通讯录
    print_address_book(head);
    
    // 保存通讯录到文件并从文件中加载
    save_address_book(head, "address_book.txt");
    address_book *new_head = load_address_book("address_book.txt");
    
    // 打印新的通讯录
    print_address_book(new_head);
    
    // 删除一个节点并打印新的通讯录
    delete_address_book(&new_head, "Bob");
    print_address_book(new_head);
    
    // 释放内存
    address_book *current = new_head;
    while (current != NULL) {
        address_book *next = current->next;
        free(current);
        current = next;
    }
    
    return 0;
}

上面的代码演示了如何使用双向链表实现一个简单的通讯录，并支持保存数据到文件以及从文件中加载数据。可以根据实际需求进行修改和扩展。