Step by Step solution about How to resolve the algorithm Validate International Securities Identification Number step by step in the C++ programming language

This C++ code is designed to check the validity of International Securities Identification Numbers (ISINs) using two helper functions: CheckFormat and CodeISIN, and then validates the ISIN using the Luhn algorithm in the CkeckISIN function. Here's a breakdown of the code:

• CheckFormat function:

  • It takes an ISIN as input and uses a regular expression (std::regex) to check if the ISIN follows a predefined format.
  • A valid ISIN must consist of 12 characters, starting with two alphabetic characters followed by nine alphanumeric characters and ending with a single numeric character.
  • The function returns true if the ISIN matches the expected format and false otherwise.

• CodeISIN function:

  • It takes an ISIN as input and converts each character to a corresponding numeric value.
  • Alphabetic characters are converted to their ASCII numeric equivalents (e.g., 'A' becomes '10'), while non-alphabetic characters are left unchanged.
  • The modified ISIN, with alphabetic characters converted to numbers, is then returned.

• CkeckISIN function:

  • It first calls CheckFormat to ensure the ISIN has the correct format.
  • If the format is valid, it calls CodeISIN to convert the ISIN to a numeric string.
  • The numeric string is then validated using the Luhn algorithm, a common checksum method used to detect errors in identification numbers.
  • The function returns true if the ISIN passes the Luhn check and false otherwise.

• main function:

  • An array of ISINs (isins) is defined for testing.
  • For each ISIN, the function calls CkeckISIN to check its validity and prints the result along with the ISIN.
  • Output:
    • The program outputs the ISINs and their validation status (true or false) for each ISIN in the test array.

#include <string>
#include <regex>
#include <algorithm>
#include <numeric>
#include <sstream>

bool CheckFormat(const std::string& isin)
{
	std::regex isinRegEpx(R"([A-Z]{2}[A-Z0-9]{9}[0-9])");
	std::smatch match;
	return std::regex_match(isin, match, isinRegEpx);
}

std::string CodeISIN(const std::string& isin)
{
	std::string coded;
	int offset = 'A' - 10;
	for (auto ch : isin)
	{
		if (ch >= 'A' && ch <= 'Z')
		{
			std::stringstream ss;
			ss << static_cast<int>(ch) - offset;
			coded += ss.str();
		}
		else
		{
			coded.push_back(ch);
		}
	}

	return std::move(coded);
}

bool CkeckISIN(const std::string& isin)
{
	if (!CheckFormat(isin))
		return false;

	std::string coded = CodeISIN(isin);
// from http://rosettacode.org/wiki/Luhn_test_of_credit_card_numbers#C.2B.2B11
	return luhn(coded);
}


#include <iomanip>
#include <iostream>

int main()
{
	std::string isins[] = { "US0378331005", "US0373831005", "U50378331005",
							"US03378331005", "AU0000XVGZA3", "AU0000VXGZA3",
							"FR0000988040" };
	for (const auto& isin : isins)
	{
		std::cout << isin << std::boolalpha << " - " << CkeckISIN(isin) <<std::endl;
	}
	return 0;
}