给这段代码添加用户管理

好的，为了添加用户管理，我们需要在代码中添加一个新的结构体来表示用户，并在主函数中添加一些新的选项，例如添加用户、显示用户、删除用户等等。

下面是修改后的代码示例：

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

#define MAX_BOOKS 100 // 最大书籍数量
#define MAX_USERS 50 // 最大用户数量

struct Book {
    int id;
    char title[50];
    char author[50];
    int is_available;
};

struct User {
    int id;
    char name[50];
};

struct Library {
    struct Book books[MAX_BOOKS];
    struct User users[MAX_USERS];
    int num_books;
    int num_users;
};

void add_book(struct Library *lib) {
    if (lib->num_books >= MAX_BOOKS) {
        printf("The library is full!\n");
        return;
    }
    
    struct Book book;
    printf("Enter book title: ");
    scanf("%s", book.title);
    printf("Enter book author: ");
    scanf("%s", book.author);
    book.id = lib->num_books + 1;
    book.is_available = 1;
    lib->books[lib->num_books++] = book;
    
    printf("Book added successfully!\n");
}

void display_books(struct Library *lib) {
    printf("%-5s %-20s %-20s %s\n", "ID", "Title", "Author", "Availability");
    for (int i = 0; i < lib->num_books; i++) {
        struct Book book = lib->books[i];
        printf("%-5d %-20s %-20s %s\n", book.id, book.title, book.author, book.is_available ? "Available" : "Not available");
    }
}

struct Book *find_book_by_id(struct Library *lib, int id) {
    for (int i = 0; i < lib->num_books; i++) {
        if (lib->books[i].id == id) {
            return &lib->books[i];
        }
    }
    return NULL;
}

void borrow_book(struct Library *lib) {
    int id;
    printf("Enter book ID: ");
    scanf("%d", &id);
    
    struct Book *book = find_book_by_id(lib, id);
    if (book == NULL) {
        printf("Book not found!\n");
        return;
    }
    
    if (!book->is_available) {
        printf("The book is not available!\n");
        return;
    }
    
    book->is_available = 0;
    printf("Book borrowed successfully!\n");
}

void return_book(struct Library *lib) {
    int id;
    printf("Enter book ID: ");
    scanf("%d", &id);
    
    struct Book *book = find_book_by_id(lib, id);
    if (book == NULL) {
        printf("Book not found!\n");
        return;
    }
    
    if (book->is_available) {
        printf("The book is already available!\n");
        return;
    }
    
    book->is_available = 1;
    printf("Book returned successfully!\n");
}

void add_user(struct Library *lib) {
    if (lib->num_users >= MAX_USERS) {
        printf("The user list is full!\n");
        return;
    }
    
    struct User user;
    printf("Enter user name: ");
    scanf("%s", user.name);
    user.id = lib->num_users + 1;
    lib->users[lib->num_users++] = user;
    
    printf("User added successfully!\n");
}

void display_users(struct Library *lib) {
    printf("%-5s %s\n", "ID", "Name");
    for (int i = 0; i < lib->num_users; i++) {
        struct User user = lib->users[i];
        printf("%-5d %s\n", user.id, user.name);
    }
}

struct User *find_user_by_id(struct Library *lib, int id) {
    for (int i = 0; i < lib->num_users; i++) {
        if (lib->users[i].id == id) {
            return &lib->users[i];
        }
    }
    return NULL;
}

void delete_user(struct Library *lib) {
    int id;
    printf("Enter user ID: ");
    scanf("%d", &id);
    
    struct User *user = find_user_by_id(lib, id);
    if (user == NULL) {
        printf("User not found!\n");
        return;
    }
    
    // 删除用户并将其后面的用户向前移动
    for (int i = 0; i < lib->num_users; i++) {
        if (lib->users[i].id == id) {
            for (int j = i + 1; j < lib->num_users; j++) {
                lib->users[j - 1] = lib->users[j];
            }
            lib->num_users--;
            printf("User deleted successfully!\n");
            return;
        }
    }
}

int main() {
    struct Library lib = {0};
    int choice;
    
    do {
        printf("\nLibrary Menu:\n");
        printf("1. Add book\n");
        printf("2. Display books\n");
        printf("3. Borrow book\n");
        printf("4. Return book\n");
        printf("5. Add user\n");
        printf("6. Display users\n");
        printf("7. Delete user\n");
        printf("8. Exit\n");
        printf("Enter your choice (1-8): ");
        scanf("%d", &choice);
        
        switch (choice) {
            case 1:
                add_book(&lib);
                break;
            case 2:
                display_books(&lib);
                break;
            case 3:
                borrow_book(&lib);
                break;
            case 4:
                return_book(&lib);
                break;
            case 5:
                add_user(&lib);
                break;
            case 6:
                display_users(&lib);
                break;
            case 7:
                delete_user(&lib);
                break;
            case 8:
                printf("Goodbye!\n");
                exit(0);
            default:
                printf("Invalid choice!\n");
        }
    } while (1);
    
    return 0;
}

希望这个修改后的代码能满足您的需求！