" Maximum Length of a Concatenated String with Unique Characters (LeetCode Problem)"

Leetcode/C++/Maximum_Length_of_a_Concatenated_String_with_Unique_Characters.cpp

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+#include <iostream>
+#include <vector>
+#include <unordered_set>
+using namespace std;
+/*
+You are given an array of strings arr. A string s is formed by the concatenation of a subsequence of arr that has unique characters.
+
+Return the maximum possible length of s.
+
+A subsequence is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.
+
+
+
+Example 1:
+
+Input: arr = ["un","iq","ue"]
+Output: 4
+Explanation: All the valid concatenations are:
+- ""
+- "un"
+- "iq"
+- "ue"
+- "uniq" ("un" + "iq")
+- "ique" ("iq" + "ue")
+Maximum length is 4.
+
+problem Link - https://leetcode.com/problems/maximum-length-of-a-concatenated-string-with-unique-characters/description/
+*/
+class Solution {
+public:
+    int maxLength(vector<string>& arr) {
+        int result = 0;
+        dfs(arr,"",0,result);
+        return result;
+    }
+    void dfs(const vector<string>&arr, const string& path,int idx,int &result){
+       if(isuniquechars(path)){
+           result = max(result,static_cast<int>(path.length()));
+       }
+       if(idx == arr.size()|| !isuniquechars(path)){
+           return ;
+       }
+       for(int i = idx ; i<arr.size();i++){
+           dfs(arr,path+arr[i],i+1,result);
+       }
+    }
+
+    bool isuniquechars(const string& s){
+        unordered_set<char> set;
+        for(char c : s){
+            if(set.count(c)){
+                return false;
+            }
+            set.insert(c);
+        }
+        return true;
+    }
+};