The International Bank Account Number (IBAN) is an internationally agreed means of identifying bank accounts across national borders with a reduced risk of propagating transcription errors.
The IBAN consists of up to 34 alphanumeric characters: first the two-letter ISO 3166-1 alpha-2 country code, then two check digits, and finally a country-specific Basic Bank Account Number (BBAN).
The check digits enable a sanity check of the bank account number to confirm its integrity even before submitting a transaction.
The task here is to validate the following fictitious IBAN: GB82 WEST 1234 5698 7654 32.
Details of the algorithm can be found on the Wikipedia page.
#include <string> #include <iostream> #include <boost/algorithm/string.hpp> #include <map> #include <algorithm> #include <cctype> using namespace boost::algorithm ; bool isValid ( const std::string &ibanstring ) { static std::map<std::string, int> countrycodes { {"AL" , 28} , {"AD" , 24} , {"AT" , 20} , {"AZ" , 28 } , {"BE" , 16} , {"BH" , 22} , {"BA" , 20} , {"BR" , 29 } , {"BG" , 22} , {"CR" , 21} , {"HR" , 21} , {"CY" , 28 } , {"CZ" , 24} , {"DK" , 18} , {"DO" , 28} , {"EE" , 20 } , {"FO" , 18} , {"FI" , 18} , {"FR" , 27} , {"GE" , 22 } , {"DE" , 22} , {"GI" , 23} , {"GR" , 27} , {"GL" , 18 } , {"GT" , 28} , {"HU" , 28} , {"IS" , 26} , {"IE" , 22 } , {"IL" , 23} , {"IT" , 27} , {"KZ" , 20} , {"KW" , 30 } , {"LV" , 21} , {"LB" , 28} , {"LI" , 21} , {"LT" , 20 } , {"LU" , 20} , {"MK" , 19} , {"MT" , 31} , {"MR" , 27 } , {"MU" , 30} , {"MC" , 27} , {"MD" , 24} , {"ME" , 22 } , {"NL" , 18} , {"NO" , 15} , {"PK" , 24} , {"PS" , 29 } , {"PL" , 28} , {"PT" , 25} , {"RO" , 24} , {"SM" , 27 } , {"SA" , 24} , {"RS" , 22} , {"SK" , 24} , {"SI" , 19 } , {"ES" , 24} , {"SE" , 24} , {"CH" , 21} , {"TN" , 24 } , {"TR" , 26} , {"AE" , 23} , {"GB" , 22} , {"VG" , 24 } } ; std::string teststring( ibanstring ) ; erase_all( teststring , " " ) ; //defined in boost/algorithm/string.hpp if ( countrycodes.find( teststring.substr(0 , 2 )) == countrycodes.end( ) ) return false ; if ( teststring.length( ) != countrycodes[ teststring.substr( 0 , 2 ) ] ) return false ; if ( ! ( all ( teststring , is_alnum( ) ) ) ) return false ; to_upper( teststring ) ; teststring = teststring.append( teststring.substr( 0 , 4 ) ) ; teststring.assign( teststring.substr( 4 ) ) ; std::string numberstring ;//will contain the letter substitutions for ( int i = 0 ; i < teststring.length( ) ; i++ ) { if ( std::isdigit( teststring[ i ] ) ) numberstring = numberstring + teststring[ i ] ; if ( std::isupper( teststring[ i ] ) ) numberstring = numberstring + std::to_string( static_cast<int>( teststring[ i ] ) - 55 ) ; } //implements a stepwise check for mod 97 in chunks of 9 at the first time // , then in chunks of seven prepended by the last mod 97 operation converted //to a string int segstart = 0 ; int step = 9 ; std::string prepended ; long number = 0 ; while ( segstart < numberstring.length( ) - step ) { number = std::stol( prepended + numberstring.substr( segstart , step ) ) ; int remainder = number % 97 ; prepended = std::to_string( remainder ) ; if ( remainder < 10 ) prepended = "0" + prepended ; segstart = segstart + step ; step = 7 ; } number = std::stol( prepended + numberstring.substr( segstart )) ; return ( number % 97 == 1 ) ; } int main( ) { std::cout << "GB82 WEST 1234 5698 7654 32 is " << ( isValid( "GB82 WEST 1234 5698 7654 32" ) ? "" : "not " ) << "valid!" << std::endl ; std::cout << "GB82TEST12345698765432 is " << ( isValid( "GB82TEST12345698765432" ) ? "" : "not " ) << "valid!" << std::endl ; return 0 ; }
- Output:
GB82 WEST 1234 5698 7654 32 is valid! GB82TEST12345698765432 is not valid!
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