Java backtracking simple & easy understanding
Github link please start the repo :  https://github.com/chiranjeevisaride/leetcode/blob/master/1239.%20Maximum%20Length%20of%20a%20Concatenated%20String%20with%
Github link please start the repo :  https://github.com/chiranjeevisaride/leetcode/blob/master/1239.%20Maximum%20Length%20of%20a%20Concatenated%20String%20with%20Unique%20Characters.java\nTime - O(n*2^n) Space: O(n)\n\n```\nclass Solution {\n    public int maxLength(List<String> arr) {\n        int[] result = new int[1];\n        getMaxLength(0, arr, "", result); \n        return result[0];\n    }\n    \n    public void getMaxLength(int index, List<String> arr, String currentStr, int[] maxLenth) {\n        if(index == arr.size()) {\n            if(uniqueCharCount(currentStr) > maxLenth[0])\n                maxLenth[0] = currentStr.length();\n            return;\n        }\n       \n        getMaxLength(index + 1, arr, currentStr + arr.get(index), maxLenth);\n        getMaxLength(index + 1, arr, currentStr, maxLenth);\n    }\n    \n    public int uniqueCharCount(String currentStr) {\n      int[] count = new int[26];\n        for(char c : currentStr.toCharArray()) \n            if(count[ c - \'a\']++ > 0) return -1;\n           return currentStr.length();\n    }\n}\n```
['Backtracking', 'Java']