can someone tell me how this program works? I'm trying to learning C++ by reading some examples, and this one is one of them.
#include <iostream>
#include <string>
using namespace std;
class Vigenere
{
public:
string key;
Vigenere(string key)
{
for(int i = 0; i < key.size(); ++i)
{
if(key[i] >= 'A' && key[i] <= 'Z')
this->key += key[i];
else if(key[i] >= 'a' && key[i] <= 'z')
this->key += key[i] + 'A' - 'a';
}
}
string encrypt(string text)
{
string out;
for(int i = 0, j = 0; i < text.length(); ++i)
{
char c = text[i];
if(c >= 'a' && c <= 'z')
c += 'A' - 'a';
else if(c < 'A' || c > 'Z')
continue;
out += (c + key[j] - 2*'A') % 26 + 'A';
j = (j + 1) % key.length();
}
return out;
}
string decrypt(string text)
{
string out;
for(int i = 0, j = 0; i < text.length(); ++i)
{
char c = text[i];
if(c >= 'a' && c <= 'z')
c += 'A' - 'a';
else if(c < 'A' || c > 'Z')
continue;
out += (c - key[j] + 26) % 26 + 'A';
j = (j + 1) % key.length();
}
return out;
}
};
int main()
{
Vigenere cipher("VIGENERECIPHER");
string original = "Beware the Jabberwock, my son! The jaws that bite, the claws that catch!";
string encrypted = cipher.encrypt(original);
string decrypted = cipher.decrypt(encrypted);
cout << original << endl;
cout << "Encrypted: " << encrypted << endl;
cout << "Decrypted: " << decrypted << endl;
}thanks
