1889A - Qingshan Loves Strings 2 - CodeForces Solution

#include<iostream>
#include<bits/stdc++.h>
#include<math.h>
#define ll long long
using namespace std;


void solve()
{
    int n;
    string s;
    cin>>n;
    cin>>s;
    int count1=0,count0=0;
    for(auto i:s)
    {
        if(i=='1')
        {count1++;}
        else{
            count0++;
        }
    }

    if(count1!=count0)
    {
        cout<<-1<<endl;
    }
    else{
        int l=0,r=s.size()-1;
        string s2="01";
        vector<int> ans;
        int count=0;
        
        while(l<r)
        {
            if(s[l]==s[r])
            {   
                if(s[l]=='1')
                {
                    s.insert(l,s2);
                    ans.push_back(l);
                }
                else{
                    s.insert(r+1,s2);
                    ans.push_back(r+1);
                }
                
                count++;
                
                l=0;
                r=s.size()-1;
            }
            else{
                l++;
                r--;
            }

            
        }
        if(count>300)
        {
            cout<<-1<<endl;
            return;
        }
        cout<<ans.size()<<endl;
        for(auto i:ans)
        {
            cout<<i<<" ";
        }

        cout<<endl;



    }





}

int main()
{
    int t=1;
    cin>>t;
    while(t--)
    {
        solve();
    }


    return 0;
}