void add_comment_to_book(int book_index) { int comment_id = num_comments; comments[num_comments].id = comment_id; comments[num_comments].book_id = book_index; printf("请输入评论："); getchar(); // 消耗掉之前输入的回车符 fgets(comments[num_comments].text, sizeof(comments[num_comments].text), stdin); comments[num_comments].text[strlen(comments[num_comments].text)-1] = '\0'; book[book_index].commentids[book[book_index].commentcount] = comment_id; book[book_index].commentcount++; num_comments++; printf("评论成功！\n");改进用户可以多次评论

可以在函数中添加一个循环，让用户可以多次评论，直到用户输入指定的结束标志才退出循环，比如可以在每次评论后询问用户是否继续评论，如果用户输入是，则继续评论，如果输入否，则退出循环。具体实现可以参考下面的代码示例：

void add_comment_to_book(int book_index) {
    int comment_id;
    char continue_flag = 'Y';
    do {
        comment_id = num_comments;
        comments[num_comments].id = comment_id;
        comments[num_comments].book_id = book_index;
        printf("请输入评论：");
        getchar(); // 消耗掉之前输入的回车符
        fgets(comments[num_comments].text, sizeof(comments[num_comments].text), stdin);
        comments[num_comments].text[strlen(comments[num_comments].text)-1] = '\0';
        book[book_index].commentids[book[book_index].commentcount] = comment_id;
        book[book_index].commentcount++;
        num_comments++;
        printf("评论成功！\n");
        printf("是否继续评论？（Y/N）");
        scanf("%c", &continue_flag);
        getchar(); // 消耗掉之前输入的回车符
    } while (continue_flag == 'Y' || continue_flag == 'y');
}