Remove invalid parentheses - cpp solution to review

RemoveInvalideParenthese.cpp

class Solution {
public:

    bool isParen(char ch)
    {
        return ch == ')' || ch == '(';
    }
    
    bool isValid(string s)
    {
        // if(s.size() == 0)
        //     return false;
            
        int closeParencount = 0;
        
        
        for(auto ch : s)
        {
            if(isParen(ch))
            {
                if(ch == ')')
                    closeParencount--;
                else
                    closeParencount++;
                
                if(closeParencount < 0)
                    return false;
            }
        }
        
        return closeParencount == 0;
   }
   
    vector<string> removeInvalidParentheses(string s){
        
       bool perfectstrlenfound = false;
       
       vector<string> res;
       queue<string> Q;//front and then pop
       
       unordered_set<string> UM;//for checking the duplicatoin.
        
        if(s.size() == 0)
        {
            res.push_back("");
            return res;//.emplace_back("");
        }
            
        
       if(isValid(s))
       {
           res.push_back(s);
           return res;
       }
       
       Q.push(s);
       
       
       while(!Q.empty())
       {
           
           string curstr = Q.front();
           Q.pop();
           
           //cout << " curstr is " << curstr << endl;
           if(isValid(curstr))
           {
               //cout << "Found the perfect string " << curstr ;
               
               res.push_back(curstr);
               
               perfectstrlenfound = true;
               continue;
               
           }
           
           if(perfectstrlenfound)
                continue;
                
           for(int i = 0; i < curstr.size(); i++)
           {
               if(!isParen(curstr[i]))
                    continue;
                    
               string newstr = curstr.substr(0,i) + curstr.substr(i+1);
               
              // cout << "newstr is " << newstr << endl;
               
               if(!UM.count(newstr))
               {
                   Q.push(newstr);
                   UM.insert(newstr);
               }
           }                    
       }
       
       return res;    
    }
};