I've been working on this pset for a few weeks now and can't seem to figure out how to correctly apply modulo to wrap my cipher. When I run my program, I correctly cipher the first time around, think I correctly advance only for chars, but then I'm stuck...any thoughts/advice?
for (int i = 0, count = 0, j = strlen(text); i < j; i++) //for each letter of original text
{
if (isalpha(text[i]))
{
if (isupper(text[i])) //TEXT IS UPPER
{
if (isupper(key[i])) // key is UPPER
{
int shift = (key[count] - 'A') % 26;
printf("%c", (((text[i] - 'A') + shift) % 26) + 'A');
}
if (islower(key[i])) //key is lower
{
int shift = (key[count] - 'a');
printf("%c", (((text[i] - 'A') + shift) % 26) + 'A');
}
}
else if (islower(text[i])) //apply shift to lower letters
{
if (isupper(key[i])) //print uppers
{
int shift = (key[count] - 'A') % 26;
printf("%c", (((text[i] - 'a') + shift) % 26) + 'a');
}
if (islower(key[i])) //print lowers
{
int shift = ((key[count] - 'a') % 26);
printf("%c", (((text[i] - 'a') + shift) % 26) + 'a');
}
}
count++;
count = count % len;
}
if (!isalpha(text[i]))
{
printf("%c", text[i]);
}
}
