The International Standard Book Number (ISBN) is a unique numeric book identifier which is printed on every book. The ISBN is based upon a 10-digit code.
The ISBN is legal if:
1 × digit1 + 2 × digit2 + 3 × digit3 + 4 × digit4 + 5 × digit5 + 6 × digit6 + 7 × digit7 + 8 × digit8 + 9 × digit9 + 10 × digit10 is divisible by 11.
Example:
For an ISBN 1401601499
Sum = 1 × 1 + 2 × 4 + 3 × 0 + 4 × 1 + 5 × 6 + 6 × 0 + 7 × 1 + 8 × 4 + 9 × 9 + 10 × 9 = 253 which is divisible by 11.
Write a program to:
import java.util.Scanner;
public class RAnsariISBNCheck
{
public static void main(String args[]) {
Scanner in = new Scanner(System.in);
System.out.print("Enter the ISBN: ");
long isbn = in.nextLong();
int sum = 0, count = 0, m = 10;
while (isbn != 0) {
int d = (int)(isbn % 10);
count++;
sum += d * m;
m--;
isbn /= 10;
}
if (count != 10) {
System.out.println("Illegal ISBN");
}
else if (sum % 11 == 0) {
System.out.println("Legal ISBN");
}
else {
System.out.println("Illegal ISBN");
}
}
}
Enter the ISBN: 1401601499
Legal ISBN
Press any key to continue . . .
Enter the ISBN: 140166444
Illegal ISBN
Press any key to continue . . .
First understand the algorithm carefully. Then study the program line-by-line and compare it with the output. Finally, review the explanation section to strengthen your logic and programming understanding.
Rewrite the program without looking at the code. Modify values, conditions or logic and run it again. This helps improve confidence and strengthens coding skills much faster.