Question

can some one explain the logic of how a structered linked list would work with a librarybmanagement system project in c++. would would be a way where anlinked list is implemented

Answer 1

here is the answer.............

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

// Copied from
// https://stackoverflow.com/questions/35103745/read-a-string-as-an-input-using-scanf
void flush() {
int c;
while ((c = getchar()) != '\n' & amp; & amp; c != EOF);
}

typedef struct {
char username[15];
char password[15];
}
User;

typedef struct {
int id; // must be unique
char title[50];
char author[50]; // if more than two, separate using ,(COMMA)
char ISBN[50];
char category[50];
char publication[50];
char description[255];
int taken;
}
Book;

int main() {
char option, admin_option, username[15], password[15], edit_option;
int first_time, c, i, j, id, found;
FILE * f;
User user;
Book book;

f = fopen("librarian.check", "r");
if (f == NULL) {
fclose(f);
f = fopen("librarian.check", "w");
fputc(1, f);
fclose(f);
} else {
fclose(f);
}

f = fopen("id.check", "r");
if (f == NULL) {
fclose(f);
f = fopen("id.check", "w");
fputc(0, f);
fclose(f);
} else {
fclose(f);
}

printf("Log in as \n");
printf("1: Librarian\n");
printf("2: Student\n");
printf("3: Exit\n");
printf("Enter your choice: ");
scanf("%c", & amp; option);
switch (option) {
case '1':
f = fopen("librarian.check", "r");
if (f == NULL) {
printf("Couldn't read file\n");
exit(0);
} else {
first_time = fgetc(f);
if (first_time == 1) {
fclose(f);
flush();
printf("Provide username and password to setup\n");
printf("Username (14 characters max): ");
fgets(user.username, 15, stdin);
printf("Password (14 characters max): ");
fgets(user.password, 15, stdin);

// write this credential to file
f = fopen("credential.bin", "wb");
if (f == NULL) {
printf("Someting went wrong!!\n");
exit(0);
}
fwrite( & amp; user, sizeof(User), 1, f);
fclose(f);
printf("Exit and login again to continue\n");
f = fopen("librarian.check", "w");
fputc(0, f);
fclose(f);
} else {
fclose(f);
flush();
printf("Provide credential to login\n");
printf("Username: ");
fgets(username, 15, stdin);
printf("Password: ");
fgets(password, 15, stdin);

// read the credential from file
f = fopen("credential.bin", "rb");
if (f == NULL) {
printf("Someting went wrong!!\n");
exit(0);
}
fread( & amp; user, sizeof(User), 1, f);
if (strcmp(username, user.username) != 0 || strcmp(password, user.password) != 0) {
printf("Username or password invalid\n");
exit(0);
}
printf("Login Successful!!\n");
printf("1: Add Book\n");
printf("2: Search Book\n");
printf("3: Edit Book\n");
printf("4: Delete Book\n");
printf("4: Moderate Student Request\n");
printf("Enter your choice: ");
scanf("%c", & amp; admin_option);
switch (admin_option) {
case '1':
flush();
printf("Provide the following information\n");
printf("Title: ");
fgets(book.title, 50, stdin);
printf("Author: ");
fgets(book.author, 50, stdin);
printf("ISBN: ");
fgets(book.ISBN, 50, stdin);
printf("Category: ");
fgets(book.category, 50, stdin);
printf("Publication: ");
fgets(book.publication, 50, stdin);
printf("Description: ");
fgets(book.description, 50, stdin);
book.taken = 0;

// increment ID
f = fopen("id.check", "r");
if (f == NULL) {
printf("Someting went wrong\n");
exit(1);
}

id = fgetc(f);
fclose(f);
book.id = id;

// save the record
f = fopen("book.record", "a");
fwrite( & amp; book, sizeof(Book), 1, f);
fclose(f);

id++;
f = fopen("id.check", "w");
fputc(id, f);
fclose(f);

printf("Book insertion Successful!!\n");
break;
case '2':
printf("Enter the book id to search: ");
scanf("%d", & amp; id);

// search in the database
f = fopen("book.record", "rb");
found = 0;
i = 0;
while (fread( & amp; book, sizeof(Book), 1, f)) {
if (book.id == id) {
// matched
found = 1;
printf("Book Found!!\n");
printf("Title: %s", book.title);
printf("Author: %s", book.author);
printf("ISBN: %s", book.ISBN);
printf("Category: %s", book.category);
printf("Publication: %s", book.publication);
printf("Description: %s", book.description);
break;
}
i++;
}
if (found == 0) {
printf("Sorry!! The book is not in the database\n");
}
fclose(f);
break;
case '3':
printf("Enter the book id to edit: ");
scanf("%d", & amp; id);
f = fopen("book.record", "rb+");
found = 0;
while (fread( & amp; book, sizeof(Book), 1, f)) {
if (book.id == id) {
// matched
found = 1;
break;
}
}
if (found == 0) {
printf("Sorry!! The book is not in the database\n");
} else {
printf("What field do you want to edit:\n");
printf("1. Title\n");
printf("2. Author\n");
printf("3. ISBN\n");
printf("4. Category\n");
printf("5. Publication\n");
printf("6. Description\n");
printf("Enter your choice: ");
scanf("\n%c", & amp; edit_option);
switch (edit_option) {
case '1':
flush();
printf("Enter new title: ");
fgets(book.title, 50, stdin);
break;
case '2':
printf("Enter new author: ");
fgets(book.author, 50, stdin);
break;
case '3':
printf("Enter new ISBN: ");
fgets(book.ISBN, 50, stdin);
break;
case '4':
printf("Enter new Category: ");
fgets(book.category, 50, stdin);
break;
case '5':
printf("Enter new Publication: ");
fgets(book.publication, 50, stdin);
break;
printf("Enter new Description: ");
fgets(book.description, 255, stdin);
break;
default:
printf("Enter 1 to 6\n");
break;
}
fseek(f, i, SEEK_SET);
fwrite( & amp; book, sizeof(Book), 1, f);
fclose(f);
printf("Book record modified in the database!!\n");
}
break;
case '4':
printf("Enter the book id to Delete: ");
scanf("%d", & amp; id);
f = fopen("book.record", "rb");
found = 0;
while (fread( & amp; book, sizeof(Book), 1, f)) {
if (book.id == id) {
// matched
found = 1;
break;
}
}
fclose(f);
if (found == 0) {
printf("Sorry!! The book is not in the database\n");
} else {
// create a temporary file
FILE * temp;
temp = fopen("book.temp", "a");
if (temp == NULL) {
printf("Something went wrong\n");
exit(1);
}

f = fopen("book.record", "rb");

// copy all the items except item to delete
// to temporary file
while (fread( & amp; book, sizeof(Book), 1, f)) {
if (book.id != id)
fwrite( & amp; book, sizeof(Book), 1, temp);
}
fclose(f);
fclose(temp);

// delete original file
remove("book.record");

// rename the temporary file
rename("book.temp", "book.record");
printf("Book record deleted from the database!!\n");
}
break;
default:
printf("Enter only 1 - 4\n");
break;
}
}
}

break;
case '2':
printf("Enter the book id to search: ");
scanf("%d", & amp; id);

// search in the database
f = fopen("book.record", "rb");
found = 0;
i = 0;
while (fread( & amp; book, sizeof(Book), 1, f)) {
if (book.id == id) {
// matched
found = 1;
printf("Book Found!!\n");
printf("Title: %s", book.title);
printf("Author: %s", book.author);
printf("ISBN: %s", book.ISBN);
printf("Category: %s", book.category);
printf("Publication: %s", book.publication);
printf("Description: %s", book.description);
printf("Status: ");
if (book.taken == 1) {
printf("Not Available");
} else {
printf("Available\n");
}
break;
}
i++;
}
if (found == 0) {
printf("Sorry!! The book is not in the database\n");
}
fclose(f);
break;
case '3':
printf("Bye!!\n");
exit(0);
default:
printf("Enter either 1 or 2 only\n");
break;
}
return 0;
}