My code works properly, except that it doesn't reject numeric key. I try using an if statement to validate input key as follow:
int main (int argc, string argv[]) { if((argc != 2) || (isalnum(argv[1])))
{
printf("type: ./vigenere key\n");
return 1;
}
What am I doing wrong? error message: \ expected output, not standard error of "/opt/sandbox50/bin/run.sh: line 31: 277..." https://sandbox.cs50.net/checks/ec152b9d69f345799f07e92002b15dee