Palindrome free strings KickStart question

I was reading the solution of the question asked in Google Kickstart 2022 titled Palindrome Free Strings . The problem statement can be found in the link (https://codingcompetitions.withgoogle.com/kickstart/round/00000000008cb33e/00000000009e762e). Below is the correct C++ code that passed all the tests.

#include<bits/stdc++.h>
using namespace std;
#define ll long long
bool palindrome(string a){
    ll i, l, f=0;
    
    l=a.size();
    
    if(l<=4){
        return true;
    }else{
        l=a.size();
        
        for(i=0; i<l/2; i++){
            if(a[i]!=a[l-i-1]){
                f++;
                break;
            }
        }
    }
    //cout<<a<<" "<<f<<"\n";
    if(f==0){
        return true;
    }else{
        return false;
    }
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    
    ll t, n, t1, i, j, l, f;
    string a, b, c;
    
    cin>>t;
    
    for(t1=1; t1<=t; t1++){
        cin>>n;
        cin>>a;
        
        f=0;
        
        queue<string> q1, q2;
        
        cout<<"Case #"<<t1<<": ";
        
        if(n<5){
            cout<<"POSSIBLE\n";
            continue;
        }
        
        if(a[0]=='?'){
            q1.push("1");
            q1.push("0");
        }else if(a[0]=='0'){
            q1.push("0");
        }else{
            q1.push("1");
        }
        
        for(i=1; i<n; i++){
            
            while(q1.empty()==false){
                b=q1.front();
                q1.pop();
                
                l=b.size()+1;
                if(a[i]=='?'){
                    c=b+"0";
                    
                    if(l<=4){
                        q2.push(c);
                    }else if(l==5){
                        if(palindrome(c)==false){
                            q2.push(c);
                        }
                    }else{
                            if(palindrome(c)==false && palindrome(c.substr(1, l-1))==false){
                                q2.push(c.substr(1, l-1));
                            }
                        }
                    
                    
                    c=b+"1";
                    
                    if(l<=4){
                        q2.push(c);
                    }else if(l==5){
                        if(palindrome(c)==false){
                            q2.push(c);
                        }
                    }else{
                            if(palindrome(c)==false && palindrome(c.substr(1, l-1))==false){
                                q2.push(c.substr(1, l-1));
                            }
                        }
                }else{
                    c=b+a[i];
                    
                    if(l<=4){
                        q2.push(c);
                    }else if(l==5){
                        if(palindrome(c)==false){
                            q2.push(c);
                        }
                    }else{
                            if(palindrome(c)==false && palindrome(c.substr(1, l-1))==false){
                                q2.push(c.substr(1, l-1));
                            }
                        }
                }
                
            }
            //cout<<i<<"\n";
            //cout<<q2.size()<<"\n";
            while(q2.empty()==false){
                q1.push(q2.front());
                //cout<<q2.front()<<"\n";
                q2.pop();
            }
            //cout<<"\n";
            
            if(q1.empty()==true){
                f++;
                break;
            }
        }
        
        if(f==1){
            cout<<"IMPOSSIBLE\n";
        }else{
            cout<<"POSSIBLE\n";
        }
    }
}

I tried writing the above program in Java with same logic but it only passes the sample and not the test set . can you point me where I am going wrong ?

import java.util.Scanner;
import java.lang.Exception;
import java.lang.StringBuilder;
import java.util.ArrayList;
import java.util.*;
import java.util.stream.Collectors;



  
 

public class Solution 
{
    
    public static boolean palindrome(String a)
    {
        int i = 0;
        int l = 0;
        int f = 0;
        l = a.length();
        
        if (l <= 4)
            return true;
        else 
        {
            for (i = 0; i < l/2; i++)
            {
                if (a.charAt(i) != a.charAt(l-i-1))
                {
                    f++;
                    break;
                }
            }
        }
        
        if (f == 0)
            return true;
        else 
            return false;
    }
    
    public static void checkPalinfree(int first, String second, int input)
    {
        Queue<String> q1 = new LinkedList<>();
        Queue<String> q2 = new LinkedList<>();
        String b = "";
        String c = "";
        int l = 0;
        int f = 0;
        
        
        if (first < 5)
            System.out.println("Case #" + (input + 1) + ":  " + "POSSIBLE");
        
        if (second.charAt(0) == '?')
        {
            q1.add("1");
            q1.add("0");
        }
        else if (second.charAt(0) == '0')
        {
            q1.add("0");
        }
        else
        {
            q1.add("1");
        }
        
        for (int i = 1; i < first; i++)
        {
            while (q1.size() != 0)
            {
                b = q1.peek();
                q1.poll();
                l = b.length() + 1;
                if (second.charAt(i) == '?')
                {
                    c = b + "0";
                    
                    if (l <= 4)
                    {
                        q2.add(c);
                    }
                    else if (l == 5)
                    {
                        if (palindrome(c) == false)
                        {
                            q2.add(c);
                        }
                        
                    }
                    else 
                    {
                        if (palindrome(c) == false && palindrome(c.substring(1, l-1)) == false)
                        {
                            q2.add(c.substring(1,l-1));
                        }
                    }
                    
                    c = b + "1";
                    
                    if (l <= 4)
                    {
                        q2.add(c);
                    }
                    else if (l == 5)
                    {
                        if (palindrome(c) == false)
                        {
                            q2.add(c);
                        }
                        
                    }
                    else 
                    {
                        if (palindrome(c) == false && palindrome(c.substring(1, l-1)) == false)
                        {
                            q2.add(c.substring(1,l-1));
                        }
                    }
                    
                    
                }
                else 
                {
                    c = b + second.charAt(i);
                    
                    if (l <= 4)
                    {
                        q2.add(c);
                    }
                    else if (l == 5)
                    {
                        if (palindrome(c) == false)
                        {
                            q2.add(c);
                        }
                        
                    }
                    else 
                    {
                        if (palindrome(c) == false && palindrome(c.substring(1, l-1)) == false)
                        {
                            q2.add(c.substring(1,l-1));
                        }
                    }
                }
                
                
                
            }
            
            while (q2.size() != 0)
            {
                q1.add(q2.peek());
                q2.poll();
            }
            
            if (q1.size() == 0)
            {
                f++;
                break;
            }
        }
        
        if (f == 1)
        {
            System.out.println("Case #" + (input + 1) + ":  " + "IMPOSSIBLE");
        }
        else 
        {
            System.out.println("Case #" + (input + 1) + ":  " + "POSSIBLE");
        }
    }
     public static void main(String args[]) {
      
      
      Scanner myObj = new Scanner(System.in);
      int input_test_case = Integer.parseInt(myObj.nextLine());
      for (int i = 0; i < input_test_case; i++)
      {
          int first = Integer.parseInt(myObj.nextLine());
          String second = myObj.nextLine();
          checkPalinfree(first,second,i);
      }
 
  }
}