def permutations(s):
    result = []

    def permutation(s, k=None):
        global sequence
        nonlocal result

        if k == None:
            k = len(s)
            sequence = []
            sequence.extend(s)

        if k == 1:
            result.append(''.join(sequence))
            return

        for i in range(k):
            permutation(sequence, k-1)
            if k & 1:
                sequence[0], sequence[k-1] = sequence[k-1], sequence[0]
            else:
                sequence[i], sequence[k-1] = sequence[k-1], sequence[i]

    permutation(s)
    return list(set(result))