Untitled

#include<bits/stdc++.h>
using namespace std;
string generateKey(string s, string key){
    int x = s.size();

    for (int i = 0; ; i++)
    {
        if (x == i)
            i = 0;
        if (key.size() == s.size())
            break;
        key.push_back(key[i]);
    }
    return key;
}
string encryption(string s, string key) {
    string encrypted;
    int keyIndex = 0;
    for (int i = 0; i < s.size(); i++) {
        char alpha;
        if (isalpha(s[i])) {
            if (islower(s[i]))
                alpha = 'a';
            else
                alpha = 'A';
            char shifted = (s[i] - alpha + key[keyIndex] - alpha) % 26 + alpha;
            encrypted += shifted;
            keyIndex = (keyIndex + 1) % key.size(); // Move to the next character in the key
        } else {
            encrypted += s[i];
        }
    }
    return encrypted;
}
string decryption(string s,string key) {
    string decrypted;
    int keyIndex = 0;
    for (int i = 0; i < s.size(); i++) {
        char alpha;
        if (isalpha(s[i])) {
            if (islower(s[i]))
                alpha = 'a';
            else
                alpha = 'A';
            char shifted = (s[i] - alpha - (key[keyIndex] - alpha) + 26) % 26 + alpha;
            decrypted += shifted;
            keyIndex = (keyIndex + 1) % key.size(); // Move to the next character in the key
        } else {
            decrypted += s[i];
        }
    }
    return decrypted;
}
int main() {
    string key = generateKey("hello world", "Lemon");
    string encrypted = encryption("Hello world", key);
    cout <<"Encrypted: "<< encrypted << "\n";
    string decrypted = decryption(encrypted, key);
    cout<<"Decrypted: "<<decrypted;
}