Backtracking | Python | Easy
see the Successfully Accepted Submission\n\npython\nclass Solution(object):\n    def maxLength(self, arr):\n\n        def is_unique(s):\n            return len(
[see the Successfully Accepted Submission](https://leetcode.com/submissions/detail/1154352928/)\n\n```python\nclass Solution(object):\n    def maxLength(self, arr):\n\n        def is_unique(s):\n            return len(s) == len(set(s))\n\n        def backtrack(index, current, max_length):\n            max_length[0] = max(max_length[0], len(current))\n\n            for i in range(index, len(arr)):\n                if is_unique(current + arr[i]):\n                    backtrack(i + 1, current + arr[i], max_length)\n\n        max_length = [0]\n        backtrack(0, "", max_length)\n        return max_length[0]\n\n```\n\n![image](https://assets.leetcode.com/users/images/b1e4af48-4da1-486c-bc97-b11ae02febd0_1696186577.992237.jpeg)
['Python']