C语言书管理系统，结构体book中有书名和作者，构建结构体数组，实现数组初始化、 添加、删除、查询(按书名、按作者)、 输出(全部、查询结果)

下面是一个简单的C语言书籍管理系统，包括结构体的定义、结构体数组的初始化、添加、删除、查询（按书名、按作者）、输出（全部、查询结果）操作：

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

#define MAX_BOOKS 100

// 书籍结构体
struct book {
    char title[50];   // 书名
    char author[30];  // 作者
};

struct book books[MAX_BOOKS];  // 书籍结构体数组
int num_books = 0;             // 当前书籍数量

// 初始化书籍数组
void init_books() {
    num_books = 3;
    strcpy(books[0].title, "C Programming Language");
    strcpy(books[0].author, "K&R");
    strcpy(books[1].title, "The Art of Computer Programming");
    strcpy(books[1].author, "Donald Knuth");
    strcpy(books[2].title, "Structure and Interpretation of Computer Programs");
    strcpy(books[2].author, "Harold Abelson and Gerald Jay Sussman");
}

// 添加新书籍
void add_book() {
    if (num_books >= MAX_BOOKS) {
        printf("Error: too many books!\n");
        return;
    }
    printf("Enter book title: ");
    scanf("%s", books[num_books].title);
    printf("Enter book author: ");
    scanf("%s", books[num_books].author);
    num_books++;
}

// 删除书籍
void del_book() {
    char title[50];
    printf("Enter book title to delete: ");
    scanf("%s", title);
    for (int i = 0; i < num_books; i++) {
        if (strcmp(books[i].title, title) == 0) {
            // 找到匹配的书籍，将后面的书籍向前移动
            for (int j = i; j < num_books - 1; j++) {
                books[j] = books[j + 1];
            }
            num_books--;
            printf("Book deleted successfully.\n");
            return;
        }
    }
    printf("Error: book not found!\n");
}

// 按书名查询书籍
void search_by_title() {
    char title[50];
    printf("Enter book title to search: ");
    scanf("%s", title);
    printf("Search results:\n");
    for (int i = 0; i < num_books; i++) {
        if (strcmp(books[i].title, title) == 0) {
            printf("%s by %s\n", books[i].title, books[i].author);
        }
    }
}

// 按作者查询书籍
void search_by_author() {
    char author[30];
    printf("Enter book author to search: ");
    scanf("%s", author);
    printf("Search results:\n");
    for (int i = 0; i < num_books; i++) {
        if (strcmp(books[i].author, author) == 0) {
            printf("%s by %s\n", books[i].title, books[i].author);
        }
    }
}

// 输出全部书籍
void print_all_books() {
    printf("There are %d books in the library:\n", num_books);
    for (int i = 0; i < num_books; i++) {
        printf("%s by %s\n", books[i].title, books[i].author);
    }
}

int main() {
    init_books();
    int choice;
    while (1) {
        printf("\n1. Add a book\n");
        printf("2. Delete a book\n");
        printf("3. Search by title\n");
        printf("4. Search by author\n");
        printf("5. Print all books\n");
        printf("6. Exit\n");
        printf("Enter your choice (1-6): ");
        scanf("%d", &choice);
        switch (choice) {
            case 1:
                add_book();
                break;
            case 2:
                del_book();
                break;
            case 3:
                search_by_title();
                break;
            case 4:
                search_by_author();
                break;
            case 5:
                print_all_books();
                break;
            case 6:
                return 0;
            default:
                printf("Invalid choice!\n");
        }
    }
    return 0;
}

注意，这只是一个简单的示例，实际应用中可能还需要加入更多的功能和错误处理。