from typing import Counter


def _exclusive(left: str, right: str) -> bool:
    """Return if two strings don't share any characters or have duplicates.

    >>> _exclusive("abc", "def")
    True
    >>> _exclusive("abcc", "def")
    False
    >>> _exclusive("abc", "cde")
    False
    """
    counter = Counter(left) + Counter(right)
    return 1 == counter.most_common(1)[0][1]