Generate IP Addresses

//{ Driver Code Starts
#include <bits/stdc++.h>

using namespace std;


// } Driver Code Ends
/*You are required to complete this method*/

class Solution{
  public:
    bool check(string s)
    {
        int n=s.length();
        if(n<0 || n>3)
        {
            return false;
        }
        if(s[0]=='0' && n>1)
        {
            return false;
        }
        int p=stoi(s);
        if(p<0 || p>255 )
        {
            return false;
        }
        return true;
    }
    string generate(string &s,int i,int j,int k,int n)
    {
        string s1=s.substr(0,i);
        string s2=s.substr(i,j-i);
        string s3=s.substr(j,k-j);
        string s4=s.substr(k,n-k);
        if(check(s1) && check(s2) && check(s3) && check(s4))
        {
            return s1+"."+s2+"."+s3+"."+s4;
        }
        return "";
    }
    vector<string> genIp(string &s) {
        // Your code here
       vector<string> ans;
       int n=s.length();
       for(int i=1;i<n-2;i++)
       {
           for(int j=i+1;j<n-1;j++)
           {
               for(int k=j+1;k<n;k++)
               {
                   string st=generate(s,i,j,k,n);
                   if(st.size()>0)
                   {
                       ans.push_back(st);
                   }
               }
           }
       }
       return ans;

    }

};

//{ Driver Code Starts.

int main() {
    int T;
    cin >> T;
    while (T--) {
        string s;
        cin >> s;

        /*generating naively*/
        Solution obj;
        vector<string> str = obj.genIp(s);
        sort(str.begin(), str.end());
        if(str.size()==0)
            cout << -1 << "\n";
        else{
            for (auto &u : str) {
                cout << u << "\n";
            }
        }
    }
}
// } Driver Code Ends