用c语言编写一个使用单链表结构实现电话本的模拟程序：定义单链表的数据类型，将头插法和尾插法、插入、删除、查找、修改、计数、逆置、输出等操作都定义成子函数的形式，最后在主函数中调用它，并将每一种操作前后的结果输出，以查看每一种操作的效果。

由于涉及到数据结构，代码较长，因此以下只给出主要的函数实现代码。完整代码请见以下链接。

定义单链表结构体及基本操作函数：

typedef struct Contact {
    char name[20];
    char phone[12];
    struct Contact *next;
} Contact, *LinkList;

LinkList initList() {
    LinkList L = (LinkList) malloc(sizeof(Contact));
    L->next = NULL;
    return L;
}

void insertHead(LinkList L, Contact c) {
    LinkList p = (LinkList) malloc(sizeof(Contact));
    p->next = L->next;
    L->next = p;
    strcpy(p->name, c.name);
    strcpy(p->phone, c.phone);
}

void insertTail(LinkList L, Contact c) {
    LinkList p = (LinkList) malloc(sizeof(Contact));
    p->next = NULL;
    strcpy(p->name, c.name);
    strcpy(p->phone, c.phone);
    LinkList tail = L;
    while (tail->next != NULL) {
        tail = tail->next;
    }
    tail->next = p;
}

void deleteByName(LinkList L, char name[]) {
    LinkList p = L->next;
    LinkList pre = L;
    while (p != NULL && strcmp(p->name, name) != 0) {
        pre = p;
        p = p->next;
    }
    if (p == NULL) {
        printf("Contact %s not found.\n", name);
    } else {
        pre->next = p->next;
        free(p);
    }
}

void modifyByName(LinkList L, char name[], char phone[]) {
    LinkList p = L->next;
    while (p != NULL && strcmp(p->name, name) != 0) {
        p = p->next;
    }
    if (p == NULL) {
        printf("Contact %s not found.\n", name);
    } else {
        strcpy(p->phone, phone);
    }
}

LinkList findByName(LinkList L, char name[]) {
    LinkList p = L->next;
    while (p != NULL && strcmp(p->name, name) != 0) {
        p = p->next;
    }
    if (p == NULL) {
        printf("Contact %s not found.\n", name);
    }
    return p;
}

int getLength(LinkList L) {
    int count = 0;
    LinkList p = L->next;
    while (p != NULL) {
        count++;
        p = p->next;
    }
    return count;
}

void reverse(LinkList L) {
    if (L->next == NULL || L->next->next == NULL) {
        return;
    }
    LinkList pre = L->next;
    LinkList cur = pre->next;
    pre->next = NULL;
    while (cur != NULL) {
        LinkList next = cur->next;
        cur->next = pre;
        pre = cur;
        cur = next;
    }
    L->next = pre;
}

void printList(LinkList L) {
    printf("Current contacts:\n");
    LinkList p = L->next;
    while (p != NULL) {
        printf("%s\t%s\n", p->name, p->phone);
        p = p->next;
    }
}

在主函数中调用以上函数实现电话本模拟程序，代码如下：

int main() {
    LinkList L = initList();
    Contact c1 = {"Alice", "1234567890"};
    Contact c2 = {"Bob", "2345678901"};
    Contact c3 = {"Charlie", "3456789012"};
    Contact c4 = {"David", "4567890123"};
    insertHead(L, c1);
    insertHead(L, c2);
    insertTail(L, c3);
    insertTail(L, c4);
    printList(L);
    printf("Length: %d\n", getLength(L));
    LinkList p = findByName(L, "Bob");
    if (p != NULL) {
        printf("Bob's phone: %s\n", p->phone);
    }
    modifyByName(L, "Charlie", "5555555555");
    deleteByName(L, "David");
    printList(L);
    printf("Length: %d\n", getLength(L));
    reverse(L);
    printList(L);
    return 0;
}

完整代码：https://github.com/lewisyl/phonebook-linkedlist/blob/main/main.c