Caesar/PSet2/CS50

#include <cs50.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, string argv[])
{
    //the key
    int key;
    //key = atoi(argv[1]);


    //taking key value
    if (argc == 2)
    {
        key = atoi(argv[1]);
    }
    else
    {
        //nothing importsnt. just for later use -_-
        //but also helps with no command line argument
        //key = get_int("Enter key: ");
        return 1;
    }

    string pt = get_string("plaintext: ");
    char ct[strlen(pt) + 1];

    //so it will round to A, not some / or [
    key = (key % 26);

    for (int i = 0,  n = strlen(pt); i < n; i++)
    {
        if (isalpha(pt[i]))
        {
            //checking if inside the Alphabet bound

            if (((pt[i] + key) > 64 && (pt[i] + key) < 91) || ((pt[i] + key) > 96 && (pt[i] + key) < 123))
            {
                ct[i] = pt[i] + key;
            }
            else
            {
                //taking care of out of out of bound
                ct[i] = (pt[i] + key) - 26;
            }
        }
        else
        {
            ct[i] = pt[i];
        }

        ct[strlen(pt)] = '\0';

    }
    //printf("ciphertext: ");
    printf("%s%s\n", "ciphertext: ", ct);

    return 0;
}