CCreate the parity bits using the Luhn Algorithm to pre$-$check the validity of a credit card number.

From the rightmost digit, which is the check digit, moving left, double the value of every second digit; if the product of this doubling operation is greater than $9($e$.$g$.,7*2=14),$ then sum the digits of the products $($e$.$g$.,10$: $1+0=1,14$: $1+4=5).$

Take the sum of all the digits. If the total moduloLinks to an external site. $10$ is equal to $0($if the total ends in zero$)$ then the number is valid according to the Luhn formula; else it is not valid.

Assume an example of an account number $"7992739871"$ that will have a check digit added, making it of the form $7992739871$x:

Account number

$7$

$9$

$9$

$2$

$7$

$3$

$9$

$8$

$7$

$1$

x

Double every other

$7$

$18$

$9$

$4$

$7$

$6$

$9$

$16$

$7$

$2$

x

Sum of digits

$7$

$9$

$9$

$4$

$7$

$6$

$9$

$7$

$7$

$2$

$=67$

T$++$he check digit $($x$)$ is obtained by computing the sum of digits then computing $9$ times that value modulo $10($in equation form, $(67*9$ mod $10)).$ In algorithm form:

Compute the sum of the digits $(67).$

Multiply by $9(603).$

The last digit, $3,$ is the check digit. $79927398713$From the rightmost digit, which is the check digit, moving left, double the value of every second digit; if the product of this doubling operation is greater than $9$

$($e$.$g$.,7**2=14),$ then sum the digits of the products $($e$.$g$.,10$:$1+0=1,14$:$1+4=5).$

Take the sum of all the digits. If the total modulo $10$ is equal to $0($if the total ends in zero$)$ then the number is valid according to the Luhn formula; else it is

not valid.

Assume an example of an account number $"7992739871"$ that will have a check digit added, making it of the form $7992739871$x:

Account number

Double every other

Sum of digits

The check digit $($x$)$ is obtained by computing the sum of digits then computing $9$ times that value modulo $10($in equation form, $(67**9$mod$10).$ In algorithm

form:

Compute the sum of the digits $(67).$

Multiply by $9(603).$

The last digit, $3,$ is the check digit. $79927398713$

C$++$