vigenere.c

// cleaned up with counter

int main(int argc, char *argv[]){
        if(argc != 2) {
                printf("Error on input");
                exit(1);
        }
        string input = get_string("Input:");
        printf("plaintext: %s\n", input);
        printf("ciphertext: ");
        string key = argv[1];
        int len = strlen(key);
        int keys[len];
        int counter = 0;

        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[counter % (strlen(key))];
                                int convertInput = input[i] - 'A';
                                int result =  (convertInput +  convertKey) % 26 + 'A';
                                printf("%c", result);
                                counter++;
                                if(counter > len-1){
                                        counter = 0;
                                 }

                        }  else if(!isupper(input[i])) {
                                int convertKey = keys[counter % (strlen(key))];
                                int convertInput = input[i] - 'a';
                                int result =  (convertInput +  convertKey) % 26 + 'a';
                                printf("%c", result);
                                counter++;
                                if(counter > len-1){
                                        counter = 0;
                                 }

                        }
                } else if(!isalpha(input[i])) {
                        printf("%c", input[i]);
                }
        }
        printf("\n");
        return 0;
}