NB: the ROT13 cypher should not be used for real security, as it is incredibly simple to reverse (simply re-apply the cypher to the output text).
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#include <cctype>
#include <iostream>
#include <string>
/**
* \brief Apply the ROT13 algorithm to a string.
* \param source Source text to apply the algorithm to.
* \return The transformed text is returned.
*/
std::string ROT13(std::string source)
{
std::string transformed;
for (size_t i = 0; i < source.size(); ++i) {
if (isalpha(source[i])) {
if ((tolower(source[i]) - 'a') < 14)
transformed.append(1, source[i] + 13);
else
transformed.append(1, source[i] - 13);
} else {
transformed.append(1, source[i]);
}
}
return transformed;
}
int main()
{
std::string source;
std::cout << "Enter the source text: " << std::flush;
std::getline(std::cin, source);
std::cout << "Result: " << ROT13(source) << std::endl;
return 0;
}
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