c语言图书逾期还书系统,急求程序！！！简单图书馆借／还书管理子系统

以下是一个简单的 C 语言图书逾期还书系统的程序，希望能够帮助到你：

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

#define MAX_BOOKS 100

struct book {
    char title[50];
    char author[50];
    bool is_borrowed;
    int borrowed_days;
};

struct book books[MAX_BOOKS];
int num_books = 0;

void add_book() {
    if (num_books >= MAX_BOOKS) {
        printf("The library is full.\n");
        return;
    }
    printf("Enter the title of the book: ");
    scanf("%s", books[num_books].title);
    printf("Enter the author of the book: ");
    scanf("%s", books[num_books].author);
    books[num_books].is_borrowed = false;
    books[num_books].borrowed_days = 0;
    num_books++;
    printf("The book has been added to the library.\n");
}

void borrow_book() {
    char title[50];
    printf("Enter the title of the book you want to borrow: ");
    scanf("%s", title);
    for (int i = 0; i < num_books; i++) {
        if (strcmp(books[i].title, title) == 0) {
            if (books[i].is_borrowed) {
                printf("The book is already borrowed.\n");
                return;
            }
            books[i].is_borrowed = true;
            books[i].borrowed_days = 0;
            printf("You have borrowed the book.\n");
            return;
        }
    }
    printf("The book is not in the library.\n");
}

void return_book() {
    char title[50];
    printf("Enter the title of the book you want to return: ");
    scanf("%s", title);
    for (int i = 0; i < num_books; i++) {
        if (strcmp(books[i].title, title) == 0) {
            if (!books[i].is_borrowed) {
                printf("The book is not borrowed.\n");
                return;
            }
            int overdue_days = books[i].borrowed_days - 30;
            if (overdue_days > 0) {
                printf("The book is %d days overdue. Please pay $%d.\n", overdue_days, overdue_days * 2);
            } else {
                printf("Thank you for returning the book.\n");
            }
            books[i].is_borrowed = false;
            books[i].borrowed_days = 0;
            return;
        }
    }
    printf("The book is not in the library.\n");
}

void print_books() {
    printf("Title\t\tAuthor\t\tBorrowed\n");
    for (int i = 0; i < num_books; i++) {
        printf("%s\t\t%s\t\t%s\n", books[i].title, books[i].author, books[i].is_borrowed ? "Yes" : "No");
    }
}

void update_books() {
    for (int i = 0; i < num_books; i++) {
        if (books[i].is_borrowed) {
            books[i].borrowed_days++;
        }
    }
}

int main() {
    int choice;
    do {
        printf("1. Add book\n");
        printf("2. Borrow book\n");
        printf("3. Return book\n");
        printf("4. Print books\n");
        printf("5. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);
        switch (choice) {
            case 1:
                add_book();
                break;
            case 2:
                borrow_book();
                break;
            case 3:
                return_book();
                break;
            case 4:
                print_books();
                break;
            case 5:
                printf("Goodbye!\n");
                break;
            default:
                printf("Invalid choice.\n");
                break;
        }
        update_books();
    } while (choice != 5);
    return 0;
}

这个程序使用一个结构体数组来存储图书的信息，包括书名、作者、是否被借阅以及借阅天数。在主函数中，使用一个 do-while 循环来读入用户的选择，并调用相应的函数来执行操作。具体来说，用户可以选择添加书籍、借阅书籍、归还书籍、打印书籍列表或退出程序。

当用户借阅一本书时，程序会将这本书的 is_borrowed 属性设置为 true，并将 borrowed_days 属性设为 0。当用户归还一本书时，程序会计算这本书被借阅的天数，如果超过了 30 天，则需要缴纳相应的罚款。注意，这里的罚款是每天 2 元。

这个程序还有许多可以改进的地方，例如可以添加更多的输入检查和错误处理机制，也可以使用链表等数据结构来存储书籍信息。但是这个程序足以满足你的需求，希望能对你有所帮助。