Question

Credit card numbers follow certain patterns. A credit card number must have between 13 and 16 digits. The number must start with the following:

4 for Visa cards

5 for MasterCard cards

37 for American Express cards

6 for Discover cards

In 1954, Hans Luhn of IBM proposed an algorithm for validating credit card numbers. The algorithm is useful to determine whether a card number is entered correctly or is scanned correctly by a scanner. Almost all credit card numbers are generated following this validity check, commonly known as the Luhn check or the Mod 10 check. It can be described as follows. (For illustration, consider the card number 4388576018402626.)

Double every second digit from right to left. If doubling of a digit results in a two-digit number, add the two digits to get a single digit number.

2*2 =4, 2*2=4, 4*2=8, 1*2=2, 6*2=12 (1+2 =3), 5*2=10 (1+0=1)

8*2= 16(1+6=7), 4*2=8

Now add all single -digit numbers from step 1.

Add all digits in the odd places from right to left in the card number.

Sum the results from step 2 and step 3.

If the result from step 4 is divisible by 10, the card number is valid; otherwise, it is invalid. For example, the number 4388576018402626 is invalid, but the number 4388576018410707 is valid.

Write a program that prompts the user to enter a credit card number as a string. Display whether the number is valid.

Your program should have at least the following functions:

bool isValid (string cardNumber ): This function returns true if the card number is valid

int sumOfDoubleEvenPlace (string cardNumber ): This function gets the result from step 2

int getDigit (int number): This function returns this number if it is a single digit, otherwise, returns the sum of the two digits

int sumOfOddPlace(string cardNumber ): This function returns the sum of odd-place digits in the card number

Do not use any global variables.

You can use function length() or size() to ?nd out the number of characters in a string and access each character in a string by its index. For example:

string word = “Hi” ;

cout <<word.size(); // displays 2

cout <<word[0]; // displays H

To convert a character into a corresponding decimal number, you can use ASCII value of the character. For example, to convert character ‘2’ into the corresponding decimal number 2, you can do the following:

int num = ‘2’ - ‘0’; // the ASCII value for ‘2’ is 50 and for ‘0’ is 48

cout <<num; // displays 2

The following example displays the sum of the numbers in a string:

        string number="2461";

            

             int sum = 0;

             for (int i = 0; i < number.size(); i++)

             {

                           sum += number[i] - '0' ;

             }

cout << sum ; // displays 13

The following example adds all digits in the odd places from right to left.

             string number="2461";

            

             int sum = 0;

             for (int i = number.size()-1; i >=0; i-=2)

             {

                           sum += number[i] - '0' ;

             }

all the program has to be followed a instruction of above and function has to be used for this program.

Thanks.

Answer 1

Given below is the code for the question.
Please do rate the answer if it was helpful. Thank you

#include <iostream>
#include <string>
using namespace std;

bool isValid (string cardNumber ) ;//This function returns true if the card number is valid
int sumOfDoubleEvenPlace (string cardNumber ); // This function gets the result of double even positioned digits and adding them up
int getDigit (int number);// This function returns this number if it is a single digit, otherwise, returns the sum of the two digits
int sumOfOddPlace(string cardNumber );// This function returns the sum of odd-place digits in the card number
int main()
{
string cardNumber;

cout << "Enter card number: ";
cin >> cardNumber;

if(isValid(cardNumber))
cout << cardNumber << " is a valid credit card number" << endl;
else
cout << cardNumber << " is NOT a valid credit card number" << endl;
}

bool isValid (string cardNumber ) //This function returns true if the card number is valid
{
int s1 = sumOfDoubleEvenPlace(cardNumber);
int s2 = sumOfOddPlace(cardNumber);
int sum = s1 + s2;
if(sum % 10 == 0)
return true;
else
return false;
}
int sumOfDoubleEvenPlace (string cardNumber ) // This function gets the result of double even positioned digits and adding them up
{
int sum = 0;
int len = cardNumber.size();
for(int i = len - 2; i >= 0; i-=2)
{
int digit = cardNumber[i] - '0'; //subtract asciii value to get int
sum = sum + getDigit(2 * digit);
}
return sum;
}
int getDigit (int number)// This function returns this number if it is a single digit, otherwise, returns the sum of the two digits
{
if (number < 10)
return number;
else
{
int d1 = number / 10;
int d2 = number % 10;
return d1 + d2;
}

}
int sumOfOddPlace(string cardNumber )// This function returns the sum of odd-place digits in the card number
{
int sum = 0;
int len = cardNumber.length();

for(int i = len-1; i >= 0; i -= 2)
{
int digit = cardNumber[i] - '0';
sum = sum + digit;
}

return sum;
}

output
-----
Enter card number: 4388576018402626
4388576018402626 is NOT a valid credit card number

Enter card number: 4388576018410707
4388576018410707 is a valid credit card number