每周挑战

def unique_number(ints: list) -> int:

    freq = counter(ints)

    only_once = [i for i in freq if freq[i] == 1]

    if len(only_once) == 1:

        return only_once[0]

    if len(only_once) == 0:

        raise valueerror('no values only appear once')

    raise valueerror('more than one value appears once')

$ ./ch-1.py 3 3 1

1

$ ./ch-1.py 3 2 4 2 4

3

$ ./ch-1.py 1

1

$ ./ch-1.py 4 3 1 1 1 4

3

def diGit_count_value(ints: list) -> bool:

    freq = counter(ints)

    for idx, value in enumerate(ints):

        if freq[idx] != value:

            return false

    return true

$ ./ch-2.py 1 2 1 0

true

$ ./ch-2.py 0 3 0

false