vigenere.c unknown problem / am I an idiot?

Question

Right gentlemen. I've been really bad doing vigenere.c, doing it for 3 days in a row, I've finally made it and it passes check50 tests, but! I've 2 almost the same codes, one which should work, but it doesn't and another one which is working, with 2 more variables which we are not using in a code. What's wrong with me? This one is working

int main (int argc, string argv[])
{
    bool argvCheck;
    string vigKey = "";

    // Checking correctness of <key> and argc arguments
    do
    {
        if (argc != 2)
        {
            printf ("Something went wrong. ./vigenere <Key>\n");
            return 1;
        }
        else if(argv[1])
        {
            for(int i = 0; i < strlen(argv[1]); i++)
            {
                if(!isalpha(argv[1][i]))
                {
                    printf("Only letters should be used as a <Key>\n");
                    return 1;
                }
                else
                {
                    argvCheck = true;
                }
            }
        }
    }
    while (argvCheck == false);

    vigKey = argv[1];

    for(int i = 0; i < strlen(vigKey);i++)
    {
        vigKey[i] = tolower(argv[1][i]);
    }

    string plainText = GetString();

    for (int i = 0, ar = 0; i < strlen(plainText); i++)
    {
        if(isalpha(plainText[i]))
        {
            if (isupper(plainText[i]))
            {
                printf ("%c", ((plainText[i] - 'A') + (argv[1][ar % strlen(argv[1])] - 'a')) % 26 + 'A');
            }
            else if (islower(plainText[i]))
            {
                printf ("%c", ((plainText[i] - 'a') + (argv[1][ar % strlen(argv[1])] - 'a')) % 26 + 'a'); 
            }
            ar++;
        }
        else
            {
                printf ("%c", plainText[i]);
            }
    }
    printf ("\n");
    return 0;
}

And this one is not working

int main (int argc, string argv[])
{
    bool argvCheck;
    //string vigKey = "";

    // Checking correctness of <key> and argc arguments
    do
    {
        if (argc != 2)
        {
            printf ("Something went wrong. ./vigenere <Key>\n");
            return 1;
        }
        else if(argv[1])
        {
            for(int i = 0; i < strlen(argv[1]); i++)
            {
                if(!isalpha(argv[1][i]))
                {
                    printf("Only letters should be used as a <Key>\n");
                    return 1;
                }
                else
                {
                    argvCheck = true;
                }
            }
        }
    }
    while (argvCheck == false);

    //vigKey = argv[1];

    /*for(int i = 0; i < strlen(vigKey);i++)
    {
        vigKey[i] = tolower(argv[1][i]);
    }*/

    string plainText = GetString();

    for (int i = 0, ar = 0; i < strlen(plainText); i++)
    {
        if(isalpha(plainText[i]))
        {
            if (isupper(plainText[i]))
            {
                printf ("%c", ((plainText[i] - 'A') + (argv[1][ar % strlen(argv[1])] - 'a')) % 26 + 'A');
            }
            else if (islower(plainText[i]))
            {
                printf ("%c", ((plainText[i] - 'a') + (argv[1][ar % strlen(argv[1])] - 'a')) % 26 + 'a'); 
            }
            ar++;
        }
        else
            {
                printf ("%c", plainText[i]);
            }
    }
    printf ("\n");
    return 0;
}

As you can see there, if I get rid of vigKey, check50 says that I'm an idiot giving me these 2 errors

:( encrypts "BaRFoo" as "CaQGon" using "BaZ" as keyword
   \ expected output, but not "=aKAoh\n"
:( encrypts "BARFOO" as "CAQGON" using "BAZ" as keyword
   \ expected output, but not "=;KA/H\n"

Answer 1

It's not so much being an idiot as it is having tunnel vision. ;-)

The problem isn't about vigKey. It's about what was done with the key string. If you look carefully at what the working code does, you'll see that the key is transformed to all lower case, so that it can be processed by subtracting 'a'. In the second version, the key isn't converted to all lower case, but it subtracts 'a' from each key letter used, even if the key letter is upper case.

You could eliminate vigKey completely and still successfully, with the following loop:

for(int i = 0, m = strlen(argv[1]); i < m; i++) 
{
    argv[1][i] = tolower(argv[1][i]);
}

If this answers your question, please click on the check mark to accept. Let's keep up on forum maintenance. ;-)