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#include <iostream>
#include <string>
using namespace std;
void GetNameAndNumber(string, int long long);
void PrintGreeting();
bool isValid(long long number);
int getSize(long long d);
int getDigit(int digit);
int sumOfDoubleEvenPlace(long long number);
int sumOfOddPlace(long long number);
int getPrefix(long long number, int k);
bool prefixMatched(long long number, int d);
int main()
{
int long long number;
string name;
// DO_4: Write a call to the function to print the greeting.
//Write a call to the function to get the name and number.
PrintGreeting();
GetNameAndNumber(name, number);
while (cin)
{
if (isValid(number))
cout << name << "'s card number " << number << " is valid."
<< endl << endl;
else
cout << name << "'s card number " << number << " is invalid."
<< endl << endl;
void GetNameAndNumber(string, int long long);
}
return 0;
}
//---------------------------------------------------------------------
// Function displays a greeting.
// params: ()
//---------------------------------------------------------------------
void PrintGreeting()
{
cout << "************************************************" << endl;
cout << "* Welcome to the credit card number validator! *" << endl;
cout << "************************************************" << endl;
}
//---------------------------------------------------------------------
// Function gets the name and card number from the user.
// params: (out, out)
//---------------------------------------------------------------------
void GetNameAndNumber(string name, int long long number)
{
cout << "Enter the name on the credit card: " << endl
<< "Ctrl+Z+Enter to quit: ";
cin >> name;
cout << endl;
cout << "Enter the credit card number, " << endl
<< "Ctrl+Z+Enter to quit: ";
cin >> number;
cout << endl;
}
//---------------------------------------------------------------------
// Function returns true if the card number is valid.
// params: (in)
//---------------------------------------------------------------------
bool isValid(long long number)
{
return (getSize(number) >= 13) && (getSize(number) <= 16) &&
(prefixMatched(number, 4) || prefixMatched(number, 5) ||
prefixMatched(number, 6) || prefixMatched(number, 37)) &&
(sumOfDoubleEvenPlace(number) +
sumOfOddPlace(number)) % 10 == 0;
}
//---------------------------------------------------------------------
// Function returns the number of digits in d.
// params: (in)
//---------------------------------------------------------------------
int getSize(long long d)
{
int counter = 0;
while (d)
{
d = d / 10;
counter++;
}
return (counter);
}
//---------------------------------------------------------------------
// Function returns this number if it is a single digit, otherwise,
// return the sum of the two digits.
// params: (in)
//---------------------------------------------------------------------
int getDigit(int digit)
{
int result = 0;
int first;
int tenths;
first = digit % 10;
tenths = digit / 10;
digit = first + tenths;
return result;
}
//---------------------------------------------------------------------
// Function returns the result from Step 2
// params: (in)
//---------------------------------------------------------------------
int sumOfDoubleEvenPlace(long long number)
{
int result = 0;
number = number / 10; // Starting from the second digit from right
while (number != 0)
{
result += getDigit(int((number % 10) * 2));
number = number / 100; // Move to the next even place
}
return result;
}
//---------------------------------------------------------------------
// Function returns the sum of odd place digits in number.
// params: (in)
//---------------------------------------------------------------------
int sumOfOddPlace(long long number)
{
long result = 0;
while (number != 0)
{
result += (number % 10);
number = number / 100; // Move two positions to the left
}
return result;
}
//---------------------------------------------------------------------
// Function returns the first k number of digits from number. If the
// number of digits in number is less than k, return number.
// params: (in)
//---------------------------------------------------------------------
int getPrefix(long long number, int k)
{
long long result = number;
int count = 0;
while (count < (getSize(number) - k))
{
result /= 10;
count++;
}
return int(result);
}
//---------------------------------------------------------------------
// Function returns true if the number d is a prefix for number.
// params: (in)
//---------------------------------------------------------------------
bool prefixMatched(long long number, int d)
{
return getPrefix(number, getSize(d)) == d;
}
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