The challenge
Given a credit card number we can determine who the issuer/vendor is with a few basic knowns.
Complete the function getIssuer() that will use the values shown below to determine the card issuer for a given card number. If the number cannot be matched then the function should return the string Unknown.
| Card Type | Begins With | Number Length |
|------------|----------------------|---------------|
| AMEX | 34 or 37 | 15 |
| Discover | 6011 | 16 |
| Mastercard | 51, 52, 53, 54 or 55 | 16 |
| VISA | 4 | 13 or 16 |
Examples
getIssuer(4111111111111111) == "VISA"
getIssuer(4111111111111) == "VISA"
getIssuer(4012888888881881) == "VISA"
getIssuer(378282246310005) == "AMEX"
getIssuer(6011111111111117) == "Discover"
getIssuer(5105105105105100) == "Mastercard"
getIssuer(5105105105105106) == "Mastercard"
getIssuer(9111111111111111) == "Unknown"
The solution in Java code
Option 1:
public class CreditCardChecker {
public static String getIssuer(String cardNumber) {
if ((cardNumber.startsWith("34") || cardNumber.startsWith("37")) && cardNumber.length()==15)
return "AMEX";
if (cardNumber.startsWith("6011") && cardNumber.length()==16)
return "Discover";
if ((cardNumber.startsWith("51") || cardNumber.startsWith("52") || cardNumber.startsWith("53") || cardNumber.startsWith("54") || cardNumber.startsWith("55")) && cardNumber.length()==16)
return "Mastercard";
if (cardNumber.startsWith("4") && (cardNumber.length()==13 || cardNumber.length()==16))
return "VISA";
return "Unknown";
}
}
Option 2:
import static java.util.regex.Pattern.matches;
public class CreditCardChecker {
public static String getIssuer(String cn) {
if (matches("^3[4|7].{13}$", cn)) return "AMEX";
if (matches("^6011.{12}$", cn)) return "Discover";
if (matches("^5[1-5].{14}$", cn)) return "Mastercard";
if (matches("^4.{12}(...)?$", cn)) return "VISA";
return "Unknown";
}
}
Option 3:
public class CreditCardChecker {
public static String getIssuer(String cardNumber) {
String visa = "4+(\\d{15}|\\d{12})";
String amex = "(34|37)+\\d{13}";
String discover = "6011+\\d{12}";
String mastercard = "(51|52|53|54|55)+\\d{14}";
String result = "Unknown";
if (cardNumber.matches(visa)) return "VISA";
if (cardNumber.matches(amex)) return "AMEX";
if (cardNumber.matches(discover)) return "Discover";
if (cardNumber.matches(mastercard)) return "Mastercard";
return result;
}
}
Test cases to validate our solution
import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;
public class SolutionTest {
@Test
public void issuerTests() {
assertEquals("VISA", CreditCardChecker.getIssuer("4111111111111111"));
assertEquals("AMEX", CreditCardChecker.getIssuer("378282246310005"));
assertEquals("Unknown", CreditCardChecker.getIssuer("9111111111111111"));
assertEquals("Mastercard", CreditCardChecker.getIssuer("5105105105105100"));
}
}
Additional test cases
import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;
import java.util.concurrent.ThreadLocalRandom;
public class SolutionTest {
@Test
public void issuerTests() {
assertEquals("VISA", CreditCardChecker.getIssuer("4111111111111111"));
assertEquals("VISA", CreditCardChecker.getIssuer("4111111111111"));
assertEquals("VISA", CreditCardChecker.getIssuer("4012888888881881"));
assertEquals("Unknown", CreditCardChecker.getIssuer("41111111111111"));
assertEquals("Unknown", CreditCardChecker.getIssuer("411111111111111"));
assertEquals("AMEX", CreditCardChecker.getIssuer("378282246310005"));
assertEquals("AMEX", CreditCardChecker.getIssuer("348282246310005"));
assertEquals("Discover", CreditCardChecker.getIssuer("6011111111111117"));
assertEquals("Mastercard", CreditCardChecker.getIssuer("5105105105105100"));
assertEquals("Mastercard", CreditCardChecker.getIssuer("5105105105105106"));
assertEquals("Mastercard", CreditCardChecker.getIssuer("5205105105105106"));
assertEquals("Mastercard", CreditCardChecker.getIssuer("5305105105105106"));
assertEquals("Mastercard", CreditCardChecker.getIssuer("5405105105105106"));
assertEquals("Mastercard", CreditCardChecker.getIssuer("5505105105105106"));
assertEquals("Unknown", CreditCardChecker.getIssuer("9111111111111111"));
assertEquals("Unknown", CreditCardChecker.getIssuer("5605105105105106"));
}
@Test
public void randomTests() {
assertEquals("VISA", CreditCardChecker.getIssuer(String.valueOf(ThreadLocalRandom.current().nextLong(4000000000000000L ,4999999999999999L ))));
assertEquals("VISA", CreditCardChecker.getIssuer(String.valueOf(ThreadLocalRandom.current().nextLong(4000000000000L ,4999999999999L ))));
assertEquals("AMEX", CreditCardChecker.getIssuer(String.valueOf(ThreadLocalRandom.current().nextLong(340000000000000L ,349999999999999L ))));
assertEquals("AMEX", CreditCardChecker.getIssuer(String.valueOf(ThreadLocalRandom.current().nextLong(370000000000000L ,379999999999999L ))));
assertEquals("Discover", CreditCardChecker.getIssuer(String.valueOf(ThreadLocalRandom.current().nextLong(6011000000000000L ,6011999999999999L ))));
assertEquals("Mastercard", CreditCardChecker.getIssuer(String.valueOf(ThreadLocalRandom.current().nextLong(5100000000000000L ,5599999999999999L ))));
assertEquals("Unknown", CreditCardChecker.getIssuer(String.valueOf(ThreadLocalRandom.current().nextLong(0L ,3999999999999L ))));
assertEquals("Unknown", CreditCardChecker.getIssuer(String.valueOf(ThreadLocalRandom.current().nextLong(6012999999999999L ,9999999999999999L ))));
}
}
