vigenere - white space throws off wrap value

Question

Having read the other posts I am still unable to solve the problem created by white space. Belows code only deals with the key as not to post too much code publically. The white space is not handled by the final else statement. I also tried inserting an if/else == ' ', but this did not work either.

int main(int argc, char *argv[]){
        if(argc != 2) {
                printf("Error on input");
                exit(1);
        }
        string input = get_string("Input:");
        string key = argv[1];
        int len = strlen(key);
        int keys[len];
        for (int i = 0; i < strlen(key); i++) {
                if(isupper(key[i])) {
                        keys[i] = key[i] - 65;
                } else {
                        keys[i] = key[i] - 97;
                }
        }

        for(int i = 0; i < strlen(input); i++) {
                if(isalpha(input[i])) {
                        // if upper case to this

                        if(isupper(input[i])) {
                                // get keys from array above
                                int convertKey = keys[i % (strlen(key))];

                                printf("%i\n", convertKey);

                        }  else if(!isupper(input[i])) {
                                int convertKey = keys[i % (strlen(key))];

                                printf("%i\n", convertKey);

                        }
                } else if(isalpha(input[i]) == false) {
                        // or !isalpha(input[i])
                        // or (isalpha == ' ')
                        printf("%c", input[i]);
                }
        }
}

When I enter:

./vigenere bacon
Meetme => 10214131
Meet me => 10214 10

Above shows wrap skips the 13, but this is not even the white space (*edit- I see that it is now actually). I think the i is accessing the incorrect element in the keys array. I don't know how to stop the wrap from moving during the space though, or know how to fix.

Answer 1

The code uses the same index, i, to control the plaintext and the key. On each pass through the loop, a plaintext char is ALWAYS consumed, but a key char is ONLY consumed when the plaintext is an alpha and NEVER when the plaintext is not an alpha. The key needs a different index var and the two indexes must be independent. Also, the key index must ONLY be incremented when an alpha is consumed from the plaintext.

Don't overthink it. There is actually a very simple solution (and it isn't a second for loop, so don't go there.)

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