python solution
\tclass Solution:\n\t\tdef maxLength(self, arr: List[str]) -> int:\n\t\t\ts = [""]\n\t\t\tres = 0\n\t\t\tfor i in arr:\n\t\t\t\tif len(set(i)) == len(i):\n\t\t\
\tclass Solution:\n\t\tdef maxLength(self, arr: List[str]) -> int:\n\t\t\ts = [""]\n\t\t\tres = 0\n\t\t\tfor i in arr:\n\t\t\t\tif len(set(i)) == len(i):\n\t\t\t\t\tfor j in s[:]:\n\t\t\t\t\t\tif len(i) + len(j) == len(set(i + j)):\n\t\t\t\t\t\t\ts.append(i + j)\n\t\t\t\t\t\t\tif len(i + j) > res:\n\t\t\t\t\t\t\t\tres = len(i + j)\n\t\t\treturn res
[]