def unique_charactors_no_data_structure(input_string):
    """Determine if a string has all unique charactors without using a data structure."""
    charactor_list = list(input_string)
    while charactor_list:
        char = charactor_list.pop(0)
        for remaining_char in charactor_list:
            if char == remaining_char:
                return False
    return True