用c语言单链表写一个通讯录系统

好的，下面是一个简单的通讯录系统的单链表实现，使用C语言编写：

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

/* 定义通讯录结构体 */
typedef struct contact {
    char name[20];
    char phone[20];
    struct contact *next;
} Contact;

/* 创建通讯录 */
Contact *create_contact() {
    Contact *head, *tail, *pnew;
    head = tail = (Contact*)malloc(sizeof(Contact));
    printf("请输入姓名：");
    scanf("%s", tail->name);
    printf("请输入电话：");
    scanf("%s", tail->phone);
    while (strcmp(tail->name, "0") != 0) {
        pnew = (Contact*)malloc(sizeof(Contact));
        printf("请输入姓名：");
        scanf("%s", pnew->name);
        if (strcmp(pnew->name, "0") == 0) {
            break;
        }
        printf("请输入电话：");
        scanf("%s", pnew->phone);
        tail->next = pnew;
        tail = pnew;
    }
    tail->next = NULL;
    return head;
}

/* 显示通讯录 */
void show_contact(Contact *head) {
    Contact *p = head;
    printf("姓名\t\t电话\n");
    while (p != NULL) {
        printf("%s\t\t%s\n", p->name, p->phone);
        p = p->next;
    }
}

/* 查找联系人 */
Contact *find_contact(Contact *head, char *name) {
    Contact *p = head;
    while (p != NULL) {
        if (strcmp(p->name, name) == 0) {
            return p;
        }
        p = p->next;
    }
    return NULL;
}

/* 添加联系人 */
Contact *add_contact(Contact *head, char *name, char *phone) {
    Contact *pnew = (Contact*)malloc(sizeof(Contact));
    strcpy(pnew->name, name);
    strcpy(pnew->phone, phone);
    pnew->next = head;
    head = pnew;
    return head;
}

/* 删除联系人 */
Contact *delete_contact(Contact *head, char *name) {
    Contact *p = head, *pre = NULL;
    while (p != NULL) {
        if (strcmp(p->name, name) == 0) {
            if (pre == NULL) {
                head = p->next;
            } else {
                pre->next = p->next;
            }
            free(p);
            return head;
        }
        pre = p;
        p = p->next;
    }
    return head;
}

/* 修改联系人 */
void modify_contact(Contact *head, char *name, char *phone) {
    Contact *p = find_contact(head, name);
    if (p != NULL) {
        strcpy(p->phone, phone);
    }
}

int main() {
    Contact *head, *p;
    char name[20], phone[20];
    int choice;
    head = create_contact();
    do {
        printf("========================\n");
        printf("1. 显示所有联系人\n");
        printf("2. 查找联系人\n");
        printf("3. 添加联系人\n");
        printf("4. 删除联系人\n");
        printf("5. 修改联系人\n");
        printf("0. 退出\n");
        printf("========================\n");
        printf("请输入选项：");
        scanf("%d", &choice);
        switch (choice) {
            case 1:
                show_contact(head);
                break;
            case 2:
                printf("请输入姓名：");
                scanf("%s", name);
                p = find_contact(head, name);
                if (p != NULL) {
                    printf("姓名\t\t电话\n");
                    printf("%s\t\t%s\n", p->name, p->phone);
                } else {
                    printf("未找到该联系人\n");
                }
                break;
            case 3:
                printf("请输入姓名：");
                scanf("%s", name);
                printf("请输入电话：");
                scanf("%s", phone);
                head = add_contact(head, name, phone);
                printf("添加成功！\n");
                break;
            case 4:
                printf("请输入姓名：");
                scanf("%s", name);
                head = delete_contact(head, name);
                printf("删除成功！\n");
                break;
            case 5:
                printf("请输入姓名：");
                scanf("%s", name);
                printf("请输入电话：");
                scanf("%s", phone);
                modify_contact(head, name, phone);
                printf("修改成功！\n");
                break;
            case 0:
                break;
            default:
                printf("输入有误，请重新输入！\n");
                break;
        }
    } while (choice != 0);
    return 0;
}

在这个例子中，我们使用单链表来实现一个简单的通讯录系统，包括创建通讯录、显示通讯录、查找联系人、添加联系人、删除联系人、修改联系人等功能。通过这个例子，您可以了解单链表在实际应用中的使用方法，并掌握基本的链表操作技巧。