请你帮忙优化一下上述代码

好的，这里给出一些优化建议：

1. 使用 fgets 函数代替 scanf 函数，可以避免输入字符串时出现空格等问题。

2. 在输入书的简介时，使用 fgets 函数，可以输入包含空格的多个单词。

3. 在输出书的信息时，使用更加清晰的格式，可以更好地展示书的信息，例如使用表格的形式。

4. 对于输入的各项信息，可以添加一些验证，确保输入的数据类型正确、输入的字符串不超过规定长度等。

5. 可以添加一些异常处理，例如输入错误时，输出相应的错误信息，而不是直接退出程序。

6. 可以使用动态数组来存储书的信息，避免书的数量达到上限后无法继续添加书的问题。

7. 可以使用文件来存储书的信息，避免程序关闭后信息丢失的问题。

下面给出一个修改后的代码，仅供参考：

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

#define MAX_DESCRIPTION 50

struct Book {
    char number[20];
    char name[50];
    char author[20];
    float price;
    int quantity;
    char description[MAX_DESCRIPTION];
};

struct Book *books = NULL;
int num_books = 0;
int max_books = 0;

void add_book()
{
    if (num_books == max_books) {
        printf("Error: the maximum number of books has been reached.\n");
        return;
    }

    struct Book new_book;

    printf("Enter the book number: ");
    fgets(new_book.number, sizeof(new_book.number), stdin);

    printf("Enter the book name: ");
    fgets(new_book.name, sizeof(new_book.name), stdin);

    printf("Enter the book author: ");
    fgets(new_book.author, sizeof(new_book.author), stdin);

    printf("Enter the book price: ");
    scanf("%f", &new_book.price);

    printf("Enter the book quantity: ");
    scanf("%d", &new_book.quantity);

    printf("Enter the book description (50 characters or less): ");
    fgets(new_book.description, sizeof(new_book.description), stdin);
    fgets(new_book.description, sizeof(new_book.description), stdin);

    if (strlen(new_book.number) == 0 || strlen(new_book.name) == 0 ||
        strlen(new_book.author) == 0 || new_book.price <= 0 ||
        new_book.quantity <= 0 || strlen(new_book.description) == 0) {
        printf("Error: invalid input.\n");
        return;
    }

    books[num_books] = new_book;
    num_books++;

    printf("The book has been added successfully.\n");
}

void search_book()
{
    char keyword[50];

    printf("Enter the keyword to search: ");
    scanf("%s", keyword);

    int found = 0;

    printf("+----------------------------------------+\n");
    printf("| %-10s | %-20s | %-10s |\n", "Book Number", "Book Name", "Book Author");
    printf("+----------------------------------------+\n");

    for (int i = 0; i < num_books; i++) {
        if (strstr(books[i].name, keyword) != NULL ||
            strstr(books[i].author, keyword) != NULL) {
            printf("| %-10s | %-20s | %-10s |\n", books[i].number, books[i].name, books[i].author);
            found = 1;
        }
    }

    printf("+----------------------------------------+\n");

    if (!found) {
        printf("No matching books found.\n");
    }
}

void list_books()
{
    if (num_books == 0) {
        printf("No books found.\n");
        return;
    }

    printf("+------------+----------------------+------------+----------+----------+----------------------+\n");
    printf("| Book Number |      Book Name       | Book Author |   Price  | Quantity |     Description      |\n");
    printf("+------------+----------------------+------------+----------+----------+----------------------+\n");

    for (int i = 0; i < num_books; i++) {
        printf("| %-10s | %-20s | %-10s | %-8.2f | %-8d | %-20s |\n",
               books[i].number, books[i].name, books[i].author,
               books[i].price, books[i].quantity, books[i].description);
    }

    printf("+------------+----------------------+------------+----------+----------+----------------------+\n");
}

void load_books()
{
    FILE *fp = fopen("books.dat", "rb");

    if (fp == NULL) {
        printf("Error: cannot open file books.dat.\n");
        return;
    }

    fread(&num_books, sizeof(int), 1, fp);

    if (num_books > 0) {
        max_books = num_books;
        books = malloc(num_books * sizeof(struct Book));
        fread(books, sizeof(struct Book), num_books, fp);
    }

    fclose(fp);
}

void save_books()
{
    FILE *fp = fopen("books.dat", "wb");

    if (fp == NULL) {
        printf("Error: cannot open file books.dat.\n");
        return;
    }

    fwrite(&num_books, sizeof(int), 1, fp);

    if (num_books > 0) {
        fwrite(books, sizeof(struct Book), num_books, fp);
    }

    fclose(fp);
}

void free_books()
{
    if (books != NULL) {
        free(books);
    }
}

int main()
{
    load_books();

    while (1) {
        printf("----------------------------------------\n");
        printf("1. Add Book\n");
        printf("2. Search Book\n");
        printf("3. List Books\n");
        printf("4. Exit\n");
        printf("----------------------------------------\n");
        printf("Enter your choice: ");

        int choice;
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                add_book();
                break;
            case 2:
                search_book();
                break;
            case 3:
                list_books();
                break;
            case 4:
                save_books();
                free_books();
                exit(0);
            default:
                printf("Error: invalid choice.\n");
                break;
        }
    }

    return 0;
}

这里使用了动态数组来存储书的信息，如果需要存储更多的书，可以通过重新分配内存来扩展数组的大小。同时，使用了文件来存储书的信息，程序启动时会从文件中读取已有的书的信息，程序退出时会将所有书的信息写入文件中。这样可以确保即使程序关闭，书的信息也不会丢失。