Write a program that prompts the user to enter a credit card number as a long integer and Display whether that card is valid or invalid.
Credit card numbers follow certain patterns.
A credit card number must have between 13 and 16 digits. It must start with:
- 4 for Visa cards
- 5 for Master cards
- 37 for American Express cards
- 6 for Discover cards
The problem can be solved by using Luhn algorithm.
Luhn check or the Mod 10 check, which can be described as follows (for illustration,
consider the card number 4388576018402626):
Step 1. Double every second digit from right to left. If doubling of a digit results in a
two-digit number, add up the two digits to get a single-digit number (like for 12:1+2, 18=1+8).
Step 2. Now add all single-digit numbers from Step 1.
4 + 4 + 8 + 2 + 3 + 1 + 7 + 8 = 37
Step 3. Add all digits in the odd places from right to left in the card number.
6 + 6 + 0 + 8 + 0 + 7 + 8 + 3 = 38
Step 4. Sum the results from Step 2 and Step 3.
37 + 38 = 75
Step 5. If the result from Step 4 is divisible by 10, the card number is valid; otherwise, it is invalid.
Input : 379354508162306 Output : 379354508162306 is Valid Input : 4388576018402626 Output : 4388576018402626 is invalid
5196081888500645 is valid
This article is contributed by Vishal Kumar Gupta. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to email@example.com. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.
Improved By : nitin mittal