利用双向链表实现通讯录的建立、删除、检索和列表，并可保存至文件，可重新装入。 c语言代码实现

在C语言中，我们可以利用双向链表数据结构来实现一个简单的通讯录功能。这里是一个基本的示例，展示了如何创建、删除、查找和保存通讯录到文件的逻辑：

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

// 定义节点结构体
typedef struct Node {
    char name[50];
    char phone[20];
    struct Node* prev;
    struct Node* next;
} Contact;

// 创建新节点
Contact* createNode(char* name, char* phone) {
    Contact* newNode = (Contact*)malloc(sizeof(Contact));
    if (newNode == NULL) {
        printf("Memory allocation failed.\n");
        return NULL;
    }
    strcpy(newNode->name, name);
    strcpy(newNode->phone, phone);
    newNode->prev = NULL;
    newNode->next = NULL;
    return newNode;
}

// 添加联系人到链表
void addContact(Contact** head, Contact* node) {
    if (*head == NULL) {
        *head = node;
    } else {
        node->prev = *head;
        (*head)->next = node;
        *head = node;
    }
}

// 删除联系人
void deleteContact(Contact** head, char* name) {
    Contact* current = *head;
    while (current != NULL && strcmp(current->name, name) != 0) {
        current = current->next;
    }

    if (current != NULL) {
        if (current->prev != NULL)
            current->prev->next = current->next;
        else
            *head = current->next;

        if (current->next != NULL)
            current->next->prev = current->prev;

        free(current);
    }
}

// 搜索并打印联系人
void searchContact(Contact* head, char* name) {
    Contact* current = head;
    while (current != NULL) {
        if (strcmp(current->name, name) == 0) {
            printf("Name: %s, Phone: %s\n", current->name, current->phone);
            break;
        }
        current = current->next;
    }
}

// 保存通讯录到文件
void saveToFile(const char* filename, Contact* head) {
    FILE* file = fopen(filename, "w");
    if (file == NULL) {
        printf("Failed to open file.\n");
        return;
    }

    Contact* current = head;
    while (current != NULL) {
        fprintf(file, "%s, %s\n", current->name, current->phone);
        current = current->next;
    }

    fclose(file);
    printf("Contacts saved to file.\n");
}

// 从文件读取并重建通讯录
Contact* loadFromFile(const char* filename) {
    Contact* head = NULL;
    FILE* file = fopen(filename, "r");
    if (file == NULL) {
        printf("Failed to open file.\n");
        return head;
    }

    char line[100], name[50], phone[20];
    while (fgets(line, sizeof(line), file)) {
        if (sscanf(line, "%s, %s", name, phone) == 2) {
            Contact* newNode = createNode(name, phone);
            if (newNode != NULL) {
                addContact(&head, newNode);
            }
        }
    }

    fclose(file);
    return head;
}

int main() {
    // 初始化链表
    Contact* contactList = NULL;

    // 添加联系人
    Contact* john = createNode("John Doe", "1234567890");
    addContact(&contactList, john);

    // 删除联系人
    deleteContact(&contactList, "John Doe");

    // 搜索并打印联系人
    searchContact(contactList, "Jane Smith"); // 示例搜索

    // 保存到文件
    saveToFile("contacts.txt", contactList);

    // 重新加载通讯录
    Contact* loadedList = loadFromFile("contacts.txt");

    // 结束前释放内存
    while (loadedList != NULL) {
        Contact* temp = loadedList;
        loadedList = loadedList->next;
        free(temp);
    }

    return 0;
}

请注意，这个示例仅作为一个基础教学用例，实际应用中可能需要处理更多的错误情况和边界条件。同时，由于C标准库对文件操作的限制，建议在生产环境中使用更可靠的文件操作函数和错误处理机制。