Szyfr Vigenere'a

#include <iostream>
#include <string>
using namespace std;

int main()
{
    int s,k, l=0;
    string slowo, klucz;
    getline(cin, slowo);
    getline(cin,klucz);
    s=slowo.length();
    k=klucz.length();
    for(int i=0; i<s; i++)
    {
        if(slowo[i]==32)
        {
            slowo[i]=' ';
        }
        else
        {
            if(l>=k)
            {
            l=0;
            }
            slowo[i]=slowo[i]-klucz[l];
            l++;

            if(slowo[i]<=0)
            {
                slowo[i]=slowo[i]+64+26;
            }
            else
            {
                slowo[i]=slowo[i]+64;
            }

        }
    }
    cout<<slowo;
}

#include <iostream>
#include <string>
using namespace std;

int main()
{
    int s,k, l=0;
    string slowo, klucz;
    getline(cin, slowo);
    cin>>klucz;
    s=slowo.length();
    k=klucz.length();
    for(int i=0; i<s; i++)
    {
        if(slowo[i]==32)
        {
            slowo[i]=' ';
        }
        else
        {
            if(l>=k)
            {
            l=0;
            }
            slowo[i]=slowo[i]+klucz[l];
            l++;

            if(slowo[i]>=155)
            {
                slowo[i]=slowo[i]-64-26;
            }
        else
        {
           slowo[i]=slowo[i]-64;
        }
        }
    }
    cout<<slowo;
}

#include <iostream>

using namespace std;

enum class MODE { ENCRYPT , DECRYPT };

template< MODE mode >
string process( const string& text , const string& key )
{
    string result;

    for( size_t i = 0 ; i < text.size() ; ++i )
    {
        result.push_back(text[i]==' '?' ':'A'+(text[i]+(mode==MODE::DECRYPT?26-key[i%key.size()]:key[i%key.size()]))%26);
    }

    return result;
}

int main()
{
    string text  { "THIS IS PLAIN TEXT" };
    string key  { "PASSWORD" };

    auto secret = process<MODE::ENCRYPT>( text , key );
    cout << secret << " -> " << process<MODE::DECRYPT>( secret , key ) << "\n";

    return 0;
}