python_黑洞数

>>> def main(n):
start = 10**(n-1)+2
end = start*10-20
for i in range(start,end):
i = str(i)
big = ‘‘.join(sorted(i,reverse=True))
big = int(big)
little = ‘‘.join(sorted(i))
little = int(little)
if big-little==int(i):
print(i)

>>> n=4
>>> main(4)
6174
>>>