cypher.cpp

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

// Function to perform encryption
string encryption(string s, int key)
{
    string output = ""; // Reset output string
    char a;

    for (int i = 0; i < s.length(); i++)
    {
        a = s[i] + key;
        // Ensure that the character remains within the range of lowercase letters or uppercase letters
        if ((s[i] >= 'a' && s[i] <= 'z') || (s[i] >= 'A' && s[i] <= 'Z'))
        {
            if ((a > 'z' && s[i] <= 'z') || (a > 'Z' && s[i] <= 'Z'))
            {
                a -= 26; // Wrap around to the beginning of the alphabet
            }
        }
        output = output + a;
    }
    return output;
}

// Function to perform decryption
string decryption(string s, int key)
{
    string output = ""; // Reset output string
    char a;

    for (int i = 0; i < s.length(); i++)
    {
        a = s[i] - key;
        // Ensure that the character remains within the range of lowercase letters or uppercase letters
        if ((s[i] >= 'a' && s[i] <= 'z') || (s[i] >= 'A' && s[i] <= 'Z'))
        {
            if ((a < 'a' && s[i] >= 'a') || (a < 'A' && s[i] >= 'A'))
            {
                a += 26; // Wrap around to the end of the alphabet
            }
        }
        output = output + a;
    }
    return output;
}

int main()
{
    string input;
    int user_choice, key;
    char choice;
    do
    {
        cout << "1) Encryption\n2) Decryption\nEnter your choice: ";
        cin >> user_choice;

        cout << endl;
        cout << "Enter text: ";
        cin.ignore(); // Ignore the newline character in the buffer
        getline(cin, input); // Allowing spaces in input

        cout << "Enter key: ";
        cin >> key;

        cout << endl;
        switch (user_choice)
        {
        case 1:
            cout << "Encrypted text: " << encryption(input, key);
            break;
        case 2:
            cout << "Decrypted text: " << decryption(input, key);
            break;
        default:
            cout << "Invalid Input!";
        }

        cout << endl
             << endl;
        cout << "Do you want to encrypt or decrypt again? (Y/N): ";
        cin >> choice;
    } while (choice == 'Y' || choice == 'y');

    return 0;
}