职工信息的综合运用 目的：深入掌握单链表应用的算法设计。 内容：设计一个职工文件emp.dat，每个职工记录包含职工号(no)、名字（name）、部门号（depno）和工资（salary）信息。设计一个程序exp2-11.cpp完成以下功能： （1）从emp.dat文件中读出职工记录，并建立一个带头结点的单链表L. (2)输入一个职工记录。 （3）显示所有职工记录。 (4)按职工号no对所有职工记录进行递增排序。 (5) 按部门号depno对所有职工记录进行递增排序。 （6）按工资salary对所有职工记录进行递增排序。 （7）删除指定职工号的职工记录。 （8）删除职工文件中的全部记录。 （9）将单链表L中所有职工记录存储到职工文件emp.dat中。

这是一个比较完整的题目，需要涉及到文件的读写、单链表的操作以及排序算法等知识点。下面是一个简单的C++程序，实现了上述要求：

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

// 定义职工信息结构体
struct Employee {
    int no;
    string name;
    int depno;
    double salary;
    Employee *next;
};

// 读取职工文件并创建职工链表
void createList(Employee *&head) {
    ifstream fin("emp.dat");
    if (!fin) {
        cout << "Failed to open file!" << endl;
        return;
    }
    Employee *p = head;
    while (!fin.eof()) {
        Employee *emp = new Employee;
        fin >> emp->no >> emp->name >> emp->depno >> emp->salary;
        emp->next = nullptr;
        p->next = emp;
        p = emp;
    }
    fin.close();
}

// 在职工链表中插入一个职工记录
void insertRecord(Employee *&head) {
    Employee *p = head;
    while (p->next != nullptr) {
        p = p->next;
    }
    Employee *emp = new Employee;
    cout << "Input employee's no, name, department number and salary: ";
    cin >> emp->no >> emp->name >> emp->depno >> emp->salary;
    emp->next = nullptr;
    p->next = emp;
}

// 显示所有职工记录
void displayList(Employee *head) {
    Employee *p = head->next;
    while (p != nullptr) {
        cout << p->no << "\t" << p->name << "\t" << p->depno << "\t" << p->salary << endl;
        p = p->next;
    }
}

// 按职工号递增排序
void sortByNo(Employee *&head) {
    Employee *p, *q, *pre, *tmp;
    pre = head;
    while (pre->next != nullptr) {
        p = pre->next;
        q = p->next;
        if (q == nullptr) {
            break;
        }
        if (p->no > q->no) {
            pre->next = q;
            p->next = q->next;
            q->next = p;
            tmp = p;
            p = q;
            q = tmp;
        }
        while (q->next != nullptr && p->no > q->next->no) {
            pre = pre->next;
            p = pre->next;
            q = p->next;
        }
    }
}

// 按部门号递增排序
void sortByDepno(Employee *&head) {
    Employee *p, *q, *pre, *tmp;
    pre = head;
    while (pre->next != nullptr) {
        p = pre->next;
        q = p->next;
        if (q == nullptr) {
            break;
        }
        if (p->depno > q->depno) {
            pre->next = q;
            p->next = q->next;
            q->next = p;
            tmp = p;
            p = q;
            q = tmp;
        }
        while (q->next != nullptr && p->depno > q->next->depno) {
            pre = pre->next;
            p = pre->next;
            q = p->next;
        }
    }
}

// 按工资递增排序
void sortBySalary(Employee *&head) {
    Employee *p, *q, *pre, *tmp;
    pre = head;
    while (pre->next != nullptr) {
        p = pre->next;
        q = p->next;
        if (q == nullptr) {
            break;
        }
        if (p->salary > q->salary) {
            pre->next = q;
            p->next = q->next;
            q->next = p;
            tmp = p;
            p = q;
            q = tmp;
        }
        while (q->next != nullptr && p->salary > q->next->salary) {
            pre = pre->next;
            p = pre->next;
            q = p->next;
        }
    }
}

// 删除指定职工号的职工记录
void deleteRecord(Employee *&head, int no) {
    Employee *p = head, *q;
    while (p->next != nullptr) {
        q = p->next;
        if (q->no == no) {
            p->next = q->next;
            delete q;
            cout << "Record deleted." << endl;
            return;
        }
        p = p->next;
    }
    cout << "Record not found." << endl;
}

// 删除职工文件中的全部记录
void deleteAllRecords() {
    ofstream fout("emp.dat");
    fout.close();
    cout << "All records deleted." << endl;
}

// 将职工链表中所有职工记录存储到职工文件中
void saveToFile(Employee *head) {
    ofstream fout("emp.dat");
    if (!fout) {
        cout << "Failed to open file!" << endl;
        return;
    }
    Employee *p = head->next;
    while (p != nullptr) {
        fout << p->no << "\t" << p->name << "\t" << p->depno << "\t" << p->salary << endl;
        p = p->next;
    }
    fout.close();
    cout << "All records saved." << endl;
}

int main() {
    Employee *head = new Employee;
    head->next = nullptr;
    createList(head);
    int choice;
    while (true) {
        cout << "1. Insert a record" << endl;
        cout << "2. Display all records" << endl;
        cout << "3. Sort by no" << endl;
        cout << "4. Sort by department number" << endl;
        cout << "5. Sort by salary" << endl;
        cout << "6. Delete a record by no" << endl;
        cout << "7. Delete all records" << endl;
        cout << "8. Save all records to file" << endl;
        cout << "0. Exit" << endl;
        cout << "Enter your choice: ";
        cin >> choice;
        switch (choice) {
            case 0:
                return 0;
            case 1:
                insertRecord(head);
                break;
            case 2:
                displayList(head);
                break;
            case 3:
                sortByNo(head);
                break;
            case 4:
                sortByDepno(head);
                break;
            case 5:
                sortBySalary(head);
                break;
            case 6:
                int no;
                cout << "Enter employee's no: ";
                cin >> no;
                deleteRecord(head, no);
                break;
            case 7:
                deleteAllRecords();
                break;
            case 8:
                saveToFile(head);
                break;
            default:
                cout << "Invalid choice." << endl;
                break;
        }
    }
    return 0;
}

需要注意的是，该程序中的排序算法都是基于插入排序实现的。在实际应用中，可以使用更高效的排序算法，例如快速排序、归并排序等。同时，该程序中的文件读写操作也比较简单，没有进行异常处理等细节处理。实际应用中，需要根据具体情况进行修改和完善。