vigenere - getting too many letters as output

Question

I was able to complete my code and it works when I "make Vigenere" however for some reason, it is outputting double the amount of letters than the plaintext. I figure it has something to do with my loop however I can´t figure it out. I would appreciate any assistance. I am attaching only the last part of my code associated with this. Thanks

 //get key 
    string key = argv[1];

    // get plaintext from user and save as plaintext variable
    {
    printf("plaintext:");
    }
    string plaintext = get_string();

    // iterate over characters in string, check upper and lower case and encrypt

    for (int i=0, j=0, n = strlen(plaintext); i < n; i++)
{   
    {
        if (isupper(plaintext[i]) && isupper(key[j]))
        {
        printf("%c", (((plaintext[i]-65) + (key[j] - 65)) % 26) + 65);        
        }

        else if (islower(plaintext[i]) && islower(key[j]))
        {
        printf("%c", (((plaintext[i]-97) + (key[j]-97)) % 26) + 97);
        }

        else if (islower(plaintext[i]) && isupper(key[j]))
        {
        printf("%c", (((plaintext[i] - 97) + (key[j] -65)) % 26) + 97);
        }

        else if (isupper(plaintext[i]) && islower(key[j]))
        {
        printf("%c", (((plaintext[i] - 65) + (key[j] - 97)) % 26) + 65);
        }
        j++;
    } 

     {
        printf("%c", plaintext[i]);
    }   
}
    printf("\n");

return 0;
}

Answer 1

The code has the large block of code that encodes the alphas, but then it is followed by the last printf statement which prints the original char whether it is an alpha or not. Seems like you might want to think about adding an isalpha check followed by an else statement. I'll let you figure out the details.

BTW, What happens when j > strlen(key)?

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