LeetCode 1239. Maximum Length of a Concatenated String with Unique Characters

class Solution {
    void fun(int idx,vector<string>& arr,vector<string>& temp,int& maxlength)
    {
        if(idx==arr.size())
        {
            string s1="";
            for(int i=0;i<temp.size();i++)
            {
                s1+=temp[i];
            }
            int freq[26]={0};
            for(int i=0;i<s1.size();i++)
            {
                freq[s1[i]-'a']++;
            }
            int cnt=0;
            for(int i=0;i<26;i++)
            {
                if(freq[i]==1)
                {
                    cnt++;
                }
                else if(freq[i]>1)
                {
                    cnt=0;
                    return;
                }
            }
            maxlength=max(maxlength,cnt);
            return;
        }
        temp.push_back(arr[idx]);
        fun(idx+1,arr,temp,maxlength);
        temp.pop_back();
        fun(idx+1,arr,temp,maxlength);
    }
public:
    int maxLength(vector<string>& arr) {
         vector<string> temp;
        int maxlength=0;
        fun(0,arr,temp,maxlength);
        return maxlength;
        
    }
};