Luhn algorithm--verification of credit card numbers

The verification of the credit card number is based on the Luhn algorithm: the old IBM engineer Hans Peter Luhn invented in 1954.

The patent was applied at that time and is now open to the public domain of knowledge as a standard for international standards organizations: ISO/EC 7812-1.

1. Starting with the last digit of the card number, the inverse adds the odd digit number to the sum
2. Starting with the last digit of the card number, multiply the even digits by 2, and if the product is a two-digit number, subtract 9 (or two-digit sum) and sum
3. The sum of odd digits is combined with the sum of even digits, and the result can be divisible by 10.

1 intLuhncheck (vector<int> &digitnums)2 {3     intSZ =digitnums.size ();4     intsum =0;5      for(intI=1; I <= sz; i++)6     {7         if(i%2==0)8         {9             intval = digitnums[sz-i] *2;Ten             if(Val >9) One             { AVal-=9; -             } -Sum + =Val; the         } -         Else -         { -Sum + = digitnums[sz-i]; +         } -     } +cout<<"Check sum:"<<sum<<Endl; A     if(sum%Ten==0) at     { -         return 1; -          } -      -}return 0;

View Code

Luhn algorithm--verification of credit card numbers