class Solution(object):
def isScramble(self, s1, s2):
"""
:type s1: str
:type s2: str
:rtype: bool
"""
n, m = len(s1), len(s2)
if n != m or sorted(s1) != sorted(s2):
return False
if n < 4 or s1 == s2:
return True
f = self.isScramble
for i in range(1, n):
if f(s1[:i], s2[:i]) and f(s1[i:], s2[i:]) or \
f(s1[:i], s2[-i:]) and f(s1[i:], s2[:-i]):
return True
return False
