C++用单链表为某个单位建立一个员工通讯录管理系统，可以方便查询每一个员工的手机号、及电子邮箱。其功能包括通讯录链表的建立、员工通讯信息的查询、修改、插入与删除、以及整个通讯录表的输出。 操作分为查询、修改、添加、删除、打印 1. 查询：输入员工姓名，输出员工信息，若员工不存在，输出“NOT FOUND!” 2. 修改：输入员工姓名、要修改的属性，修改信息。姓名为name、电话为tel、邮箱为mail。 3. 添加：输入员工编号、姓名、电话号码、邮箱。 4. 删除：输入员工姓名，将其从通讯录中删除。 5. 打印：输出通讯录。代码

下面是一个使用单链表实现员工通讯录管理系统的C++代码：

#include <iostream>
#include <string>
using namespace std;

// 定义员工结构体
struct Employee {
    int id;          // 员工编号
    string name;     // 员工姓名
    string tel;      // 员工电话号码
    string mail;     // 员工电子邮箱
    Employee* next;  // 指向下一个员工的指针
};

// 建立员工通讯录链表
Employee* createList() {
    Employee* head = new Employee;  // 头结点不存储有效数据
    head->next = NULL;
    return head;
}

// 在链表末尾添加员工信息
void addEmployee(Employee* head, int id, string name, string tel, string mail) {
    Employee* p = head;
    while (p->next != NULL) {
        p = p->next;  // 找到链表末尾
    }
    Employee* newEmployee = new Employee;
    newEmployee->id = id;
    newEmployee->name = name;
    newEmployee->tel = tel;
    newEmployee->mail = mail;
    newEmployee->next = NULL;
    p->next = newEmployee;  // 将新员工信息添加到链表末尾
}

// 根据员工姓名查询员工信息
void queryEmployee(Employee* head, string name) {
    Employee* p = head->next;
    while (p != NULL) {
        if (p->name == name) {
            cout << "ID: " << p->id << endl;
            cout << "Name: " << p->name << endl;
            cout << "Tel: " << p->tel << endl;
            cout << "Mail: " << p->mail << endl;
            return;
        }
        p = p->next;
    }
    cout << "NOT FOUND!" << endl;
}

// 根据员工姓名修改员工信息
void modifyEmployee(Employee* head, string name, string property, string value) {
    Employee* p = head->next;
    while (p != NULL) {
        if (p->name == name) {
            if (property == "name") {
                p->name = value;
            } else if (property == "tel") {
                p->tel = value;
            } else if (property == "mail") {
                p->mail = value;
            } else {
                cout << "INVALID PROPERTY!" << endl;
                return;
            }
            cout << "MODIFY SUCCESSFULLY!" << endl;
            return;
        }
        p = p->next;
    }
    cout << "NOT FOUND!" << endl;
}

// 根据员工姓名删除员工信息
void deleteEmployee(Employee* head, string name) {
    Employee* p = head->next;
    Employee* pre = head;
    while (p != NULL) {
        if (p->name == name) {
            pre->next = p->next;
            delete p;
            cout << "DELETE SUCCESSFULLY!" << endl;
            return;
        }
        pre = p;
        p = p->next;
    }
    cout << "NOT FOUND!" << endl;
}

// 输出员工通讯录信息
void printList(Employee* head) {
    Employee* p = head->next;
    while (p != NULL) {
        cout << "ID: " << p->id << endl;
        cout << "Name: " << p->name << endl;
        cout << "Tel: " << p->tel << endl;
        cout << "Mail: " << p->mail << endl;
        p = p->next;
    }
}

int main() {
    Employee* head = createList();  // 建立员工通讯录链表
    while (true) {
        cout << "1. Query employee" << endl;
        cout << "2. Modify employee" << endl;
        cout << "3. Add employee" << endl;
        cout << "4. Delete employee" << endl;
        cout << "5. Print list" << endl;
        cout << "0. Exit" << endl;
        int choice;
        cin >> choice;
        switch (choice) {
            case 1: {
                string name;
                cout << "Input employee name: ";
                cin >> name;
                queryEmployee(head, name);
                break;
            }
            case 2: {
                string name, property, value;
                cout << "Input employee name: ";
                cin >> name;
                cout << "Input property(name/tel/mail): ";
                cin >> property;
                cout << "Input new value: ";
                cin >> value;
                modifyEmployee(head, name, property, value);
                break;
            }
            case 3: {
                int id;
                string name, tel, mail;
                cout << "Input employee id: ";
                cin >> id;
                cout << "Input employee name: ";
                cin >> name;
                cout << "Input employee tel: ";
                cin >> tel;
                cout << "Input employee mail: ";
                cin >> mail;
                addEmployee(head, id, name, tel, mail);
                break;
            }
            case 4: {
                string name;
                cout << "Input employee name: ";
                cin >> name;
                deleteEmployee(head, name);
                break;
            }
            case 5: {
                printList(head);
                break;
            }
            case 0: {
                return 0;
            }
            default: {
                cout << "INVALID CHOICE!" << endl;
                break;
            }
        }
    }
    return 0;
}

注意，上述代码中的员工通讯录链表使用头结点，这是一种常见的链表实现方式。头结点不存储有效数据，只用于指向链表的第一个节点。另外，为了简化代码，我们假设员工姓名是唯一的，因此在查询、修改和删除员工信息时，只需要根据员工姓名来操作即可。