Maximum Length of a Concatenated String with Unique Characters - JavaScript solution
Intuition\nThe problem asks for finding the maximum length of a concatenation of words from the given array such that no two characters in the concatenation are
# Intuition\nThe problem asks for finding the maximum length of a concatenation of words from the given array such that no two characters in the concatenation are the same. The provided code uses a backtracking approach to explore all possible subsequences and checks if each subsequence has unique characters.\n\n# Approach\nThe code defines a function `maxLength` that takes an array of strings `arr` as input and returns the maximum length of a concatenation with unique characters. It uses a helper function `isUnique` to check if a given string has unique characters. The main backtracking function `backtrack` explores all possible subsequences by trying different combinations of words from the array.\n\nThe backtracking function takes two parameters:\n1. `start`: The index to start exploring the array.\n2. `path`: The current subsequence being built.\n\nThe base case of the backtracking function checks if the current subsequence has unique characters using the `isUnique` function. If it does, it updates the `maxLength` variable with the maximum length found so far.\n\nThe function then iterates over the array from the given `start` index, and for each element, it recursively calls itself to explore the next element in the array and build the subsequence.\n\nFinally, the `maxLength` variable is initialized to 0, and the backtracking process starts with an empty string as the initial subsequence.\n\n# Complexity\n- Time complexity: The time complexity of the backtracking approach is exponential, as it explores all possible subsequences. In the worst case, the time complexity is O(2^n), where n is the length of the input array.\n- Space complexity: The space complexity is O(n), where n is the length of the input array. This is because the backtracking function uses a recursive call stack, and the space required is proportional to the depth of the recursion.\n\n# Code\n```javascript\n/**\n * @param {string[]} arr\n * @return {number}\n */\nvar maxLength = function (arr) {\n\n    // Helper function to check if a string has unique characters\n    const isUnique = (s) => new Set(s).size === s.length;\n\n    // Backtracking function to explore all possible subsequences\n    const backtrack = (start, path) => {\n        if (isUnique(path)) {\n            // Update maxLength with the maximum length found so far\n            maxLength = Math.max(maxLength, path.length);\n        }\n        for (let i = start; i < arr.length; i++) {\n            // Explore the next element in the array to build the subsequence\n            backtrack(i + 1, path + arr[i])\n        }\n    }\n\n    // Initialize maxLength to 0 and start exploration with an empty string\n    let maxLength = 0;\n    backtrack(0, "");\n    \n    return maxLength;\n};\n```
['JavaScript']