def caesarCipher(string: str, k: int) -> str:
    if k == 0:
        return string
    vocab = "abcdefghijklmnopqrstuvwxyz"
    cipher = []
    for char in string:
        if not char.isalpha():
            cipher.append(char)
        else:
            idx = vocab.index(char.lower())   # index of character
            new_char = vocab[(idx + k) % len(vocab)]    # shift index
            # capitalise if required:
            new_char = new_char.upper() if char.isupper() else new_char 
            cipher.append(new_char)
    return "".join(cipher)