写一个飞机订票系统c语言代码，要求包含一下内容7.管理员功能：特定账号密码可以进入管理员功能界面。 8.管理员新增加机票功能：可新增加机票信息。 9.管理员修改航班信息功能。

以下是一个包含管理员功能、新增机票和修改航班信息功能的飞机订票系统的C语言代码示例：

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

#define MAX_FLIGHTS 10
#define MAX_SEATS 50

struct flight {
    int id;
    char destination[50];
    int seats[MAX_SEATS];
    int num_seats;
    int price;
};

struct flight flights[MAX_FLIGHTS];
int num_flights = 0;

void add_flight() {
    if (num_flights >= MAX_FLIGHTS) {
        printf("Maximum number of flights reached.\n");
        return;
    }

    struct flight f;
    f.id = num_flights + 1;

    printf("Enter destination: ");
    fgets(f.destination, 50, stdin);
    f.destination[strcspn(f.destination, "\n")] = 0;

    printf("Enter price: ");
    scanf("%d", &f.price);

    f.num_seats = MAX_SEATS;
    for (int i = 0; i < MAX_SEATS; i++) {
        f.seats[i] = 0;
    }

    flights[num_flights] = f;
    num_flights++;
}

void show_flights() {
    printf("Flights:\n");
    for (int i = 0; i < num_flights; i++) {
        printf("%d. %s, %d seats, $%d\n", flights[i].id, flights[i].destination, flights[i].num_seats, flights[i].price);
    }
}

void book_seat() {
    int flight_id, seat_num;
    printf("Enter flight ID: ");
    scanf("%d", &flight_id);

    if (flight_id < 1 || flight_id > num_flights) {
        printf("Invalid flight ID.\n");
        return;
    }

    struct flight *f = &flights[flight_id - 1];

    printf("Enter seat number: ");
    scanf("%d", &seat_num);

    if (seat_num < 1 || seat_num > MAX_SEATS) {
        printf("Invalid seat number.\n");
        return;
    }

    if (f->seats[seat_num - 1] == 1) {
        printf("Seat already booked.\n");
        return;
    }

    f->seats[seat_num - 1] = 1;
    f->num_seats--;

    printf("Seat booked successfully.\n");
}

void admin_menu() {
    char username[50], password[50];
    printf("Enter username: ");
    scanf("%s", username);
    printf("Enter password: ");
    scanf("%s", password);

    if (strcmp(username, "admin") == 0 && strcmp(password, "admin123") == 0) {
        int choice;
        do {
            printf("\n1. Add flight\n2. Modify flight\n3. Exit\n");
            scanf("%d", &choice);

            switch (choice) {
                case 1:
                    add_flight();
                    break;
                case 2:
                    printf("Enter flight ID: ");
                    int flight_id;
                    scanf("%d", &flight_id);
                    if (flight_id < 1 || flight_id > num_flights) {
                        printf("Invalid flight ID.\n");
                        break;
                    }

                    struct flight *f = &flights[flight_id - 1];
                    printf("Enter new destination: ");
                    fgets(f->destination, 50, stdin);
                    f->destination[strcspn(f->destination, "\n")] = 0;
                    printf("Enter new price: ");
                    scanf("%d", &f->price);
                    break;
                case 3:
                    printf("Goodbye!\n");
                    break;
                default:
                    printf("Invalid choice.\n");
                    break;
            }
        } while (choice != 3);
    } else {
        printf("Invalid username or password.\n");
    }
}

int main() {
    int choice;

    do {
        printf("\n1. Show flights\n2. Book seat\n3. Admin menu\n4. Exit\n");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                show_flights();
                break;
            case 2:
                book_seat();
                break;
            case 3:
                admin_menu();
                break;
            case 4:
                printf("Goodbye!\n");
                break;
            default:
                printf("Invalid choice.\n");
                break;
        }
    } while (choice != 4);

    return 0;
}

在这个示例中，我们添加了一个管理员菜单，只有在输入正确的用户名和密码之后才能进入。管理员可以新增机票和修改航班信息。在修改航班信息时，管理员需要输入要修改的航班的ID，然后输入新的目的地和价格。注意，在修改目的地时，我们使用了fgets函数而不是scanf函数，这是因为scanf函数会留下换行符，而fgets函数会自动将其去除。