Question

Using c++

A ten diglt ISBN number uses a checksum as its last diglt to verlfy the first nine digits are valid. Before 2007, all ISBN numbers were composed like this, such as: e-20-5e8005-7 or 1-234-56789-X The first nine digits are assigned by a book's publisher and the last digit is calculated by "weighted sum (described below). The X stands for the checksum value of 10, in order to represent ten as a single digit. You must write a program that calculates and outputs this checksum value given the first nine digits of the ISBN number, utilizing the checksum algorithm below ecksum Algorlthm To compute the weighted sum we start from the left-most digit: Sum one times the first digit, plus two times the second digit, plus three times the third, etc. all the way to nine times the ninth digit. Note: Just becouse we describe the calculation as "starting with the left-most digit" does NOT an that that is the best order for the C+ algorithml Plan carefully for the simplest way of lating each digit from the whole number. Next we take this weighted sum, and calculate the remainder after it is divided by eleven. (i.e. "weighted sum modulo eleven") Finally, the ISBN standard requires that we take this checksum digit and convert it if needed (i.e. 10 is replaced by X). We will omit this step and just output the value from 0 through 10 without any conversion. Your main function must prompt the user to enter the first 9 digits of an ISBN, and then read in that input as a single integer Your program must then calculate the corresponding checksum, and output it as shown in the example run below. Test Values (Single program execution per row) SBN (first 9-digits) 123456789 868880008 987654321 847147063 Checksum Value 16 Examples (1.1 + 2.2 + 3.3 + 4.4 + 5*5+ 6*6 + 7.7 + 8*8 + 9.9)%11-10 (1*0+ 2.0 + 3.0 + 4*0+ 5.0 + 6.0 + 7.0 + 8.0 + 9.0)%11-10 (1.9 + 2*8 + 3.7 + 4*6 + s*5+ 6.4 + 7.3 + 8.2 + 9.1)%11-0

Answer 1

The solution to the above question is given below with screenshot of output.

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I kept the logic simple and i have tested all outputs.

If there is anything else do let me know in comments.

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============ CODE TO COPY ===============================

#include<iostream>
using namespace std;

// Checking if number is valid of not
bool is_valid( long int isbn_no ){

  // if number if greater than 9 digits or negative it's invalid
  if ( isbn_no > 999999999 || isbn_no < 0  )
    return false;

  // number if ok
  return true;
}

int calculate_check( long int isbn_no ){

  int sum = 0;
  int digits = 0;

  long int temp = isbn_no;

  // count the number of digits in number
  while ( temp != 0 && ++digits )
    temp = temp/10;

  // multiply all number as per the given algo
  for ( int i = 9 ; i >= 10 - digits; i-- ){

      int rem  = isbn_no % 10;
      isbn_no = isbn_no / 10;
      sum += rem*i;
  }

  // return sum modulo 11 
  return sum % 11;
}

int main() {

  long int isbn_no = 0 ;
  int     checksum = 0 ;

  cout << "Please Enter First 9 Digits Of ISBN Number : ";
  cin  >> isbn_no;

  if ( is_valid( isbn_no ) == false )
  {
    cout << "Invalid Isbn number " << endl;
    return 0;
  }

  // here we are caclulating checksum
  checksum = calculate_check( isbn_no );
 
  cout << "Checksum is : " << checksum << endl;

  return 0;

}

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Output