Verhoeff algorithm: Difference between revisions
→{{header|C}}
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The validation for '1234567890129' is incorrect.
</pre>
=={{header|C++}}==
<syntaxhighlight>
#include <iostream>
#include <string>
typedef std::pair<std::string, bool> data;
int multiplication_table[10][10] = {
{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 },
{ 1, 2, 3, 4, 0, 6, 7, 8, 9, 5 },
{ 2, 3, 4, 0, 1, 7, 8, 9, 5, 6 },
{ 3, 4, 0, 1, 2, 8, 9, 5, 6, 7 },
{ 4, 0, 1, 2, 3, 9, 5, 6, 7, 8 },
{ 5, 9, 8, 7, 6, 0, 4, 3, 2, 1 },
{ 6, 5, 9, 8, 7, 1, 0, 4, 3, 2 },
{ 7, 6, 5, 9, 8, 2, 1, 0, 4, 3 },
{ 8, 7, 6, 5, 9, 3, 2, 1, 0, 4 },
{ 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 }
};
int inverse[10] = { 0, 4, 3, 2, 1, 5, 6, 7, 8, 9 };
int permutation_table[8][10] = {
{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 },
{ 1, 5, 7, 6, 2, 8, 3, 0, 9, 4 },
{ 5, 8, 0, 3, 7, 9, 6, 1, 4, 2 },
{ 8, 9, 1, 6, 0, 4, 3, 5, 2, 7 },
{ 9, 4, 5, 3, 1, 2, 6, 8, 7, 0 },
{ 4, 2, 8, 6, 5, 7, 3, 9, 0, 1 },
{ 2, 7, 9, 3, 8, 0, 6, 4, 1, 5 },
{ 7, 0, 4, 6, 9, 1, 3, 2, 5, 8 }
};
int verhoeff_checksum(std::string number, bool doValidation, bool doDisplay) {
if ( doDisplay ) {
std::string calculationType = doValidation ? "Validation" : "Check digit";
std::cout << calculationType << " calculations for " << number << "\n" << std::endl;
std::cout << " i ni p[i,ni] c" << std::endl;
std::cout << "------------------" << std::endl;
}
if ( ! doValidation ) {
number += "0";
}
int c = 0;
const int le = number.length() - 1;
for ( int i = le; i >= 0; i-- ) {
const int ni = number[i] - '0';
const int pi = permutation_table[(le - i) % 8][ni];
c = multiplication_table[c][pi];
if ( doDisplay ) {
printf("%2d %d %d %d\n", le - i, ni, pi, c);
}
}
if ( doDisplay && ! doValidation ) {
std::cout << "inv[" << c << "] = " << inverse[c] << "\n" << std::endl;;
}
return doValidation ? c == 0 : inverse[c];
}
int main( ) {
data tests[3] = {
std::make_pair("123", true), std::make_pair("12345", true), std::make_pair("123456789012", false) };
for ( data test : tests ) {
int digit = verhoeff_checksum(test.first, false, test.second);
std::cout << "The check digit for " << test.first << " is " << digit << "\n" << std::endl;
std::string numbers[2] = { test.first + std::to_string(digit), test.first + "9" };
for ( std::string number : numbers ) {
digit = verhoeff_checksum(number, true, test.second);
std::string result = ( digit == 1 ) ? "correct" : "incorrect";
std::cout << "The validation for " << number << " is " << result << ".\n" << std::endl;
}
}
}
</syntaxhighight>
{{ out }}
<pre>
The same as the Wren example.
</pre>
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