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error message: rejects https://sandbox.cs50.net/checks/742ebfdf355b45d594e8f23047837f51 

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

int main (int argc, string argv[])
{
    if(argc != 2)

    {
        printf("type: ./vigenere key\n");
        return 1;
    }

    string key = argv[1];
    for(int i = 0, n = strlen(key); i < n; i++)
    {
        if (!isalpha(key[i]))
        {
            printf("type program name followed by non-numeric key\n");
            return 1;
        }
    }
    //takes user plain text to encrypt
    //printf("plaintext:  ");
    string text = GetString();
    int j = 0, k_len = strlen(key);

    //printf("ciphertext:  ");
   for(int i = 0, n = strlen(text); i < n; i++)

        if(isalpha(text[i]))
        {
            if(isupper(text[i]))
            {
                char cipher = (text[i] - 'A' + key[j % k_len] - 'A') % 26; 
                j++;
                printf("%c", cipher + 'A');

            }
            if(islower(text[i]))
            {
                char cipher = (text[i] - 'a' + key[j % k_len] - 'a') % 26; 
                j++;
                printf("%c", cipher + 'a');

            }

        }
        else
        {
            printf("%c", text[i]);

        }

     printf("\n");
}
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How does your code handle the case where the plain text is lower case and the key is upper case, or the opposite?

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  • oh, I didn't realize that I was supposed to consider the capitalization of the key! Although this was helpful I'm still stuck in implementing the if loop for the key upper/lower case:
    – Jana B.W.
    Aug 7, 2016 at 18:57

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