Python问题解答的

def blackhole(n):
    res = []
    for i in range(10**(n-1),10**n):
        t = list(str(i))
        a = ''.join(sorted(t))
        b = ''.join(sorted(t, reverse=True))
        if int(b)-int(a)==i:
            res.append(i)
    for i in res:
        print(i)

以下是测试结果：
>>> blackhole(4)
6174
>>> blackhole(5)
>>> blackhole(6)
549945
631764
>>>