Coding challenge. Any ideas on how to solve it with java?

Question —



|s| is the length of string s. Form a new string b as follows.



String b is initially empty.



For each i where 1 ≤ i ≤ |s|:



Append s[i-1] to the end of b.

Reverse the string b.

Before creating b, reorder s to produce the b that is the lexicographically maximum possible.



Example

s = "011".



Reorder s from "011" to "101". String b is formed as follows.



b after

--------------

Operation Append Reverse

--------- ------ -------

1 1 1

2 10 01

3 011 110



Return "101", the permutation of s that generates the maximum possible b.



Function Description



Create the custom function with parameter that accepts String.

Returns - string: the permutation of s that generates the maximal b



Sample Case 0

Sample Input For Custom Testing



STDIN FUNCTION

----- --------

1100 → s = "1100"



Sample Output

0101



Explanation

Using the permutation "0101":



b after

--------------

Operation Append Reverse

--------- ------ -------

1 0 0

2 01 10

3 100 001

4 0011 1100

Constraints

1 ≤ |s| ≤ 10^5

The string s consists only of characters ‘0’ and ‘1’.

I also have done the research and found the code that is similar to what I am looking for but it is in C++ and I don't understand it..

   string getOptimalString(string s) {
   string ans;
   int n=s.length();
   sort(s.begin(),s.end());
   reverse(s.begin(),s.end());
   if(n%2) ans.push_back(s[n/2]);
      for(int i=(n+1)/2,j=(n-2)/2;j>=0 && i<n;j--,i++){
      ans.push_back(s[i]);
      ans.push_back(s[j]);
   }
   return ans;

//The attempt I tried below:

public static String getOptimalString(String s) {
    StringBuilder b = new StringBuilder();
    int n = s.length();

    for(int i = 0;i<n;i++){
        if(s.charAt(i)%2 == 0){
            b.append("0");
        }else{
            b.append("s.charAt(i)");}}
            b = new StringBuilder(s).reverse();return b.toString();
        }

    public static void main(String[] args) throws IOException{
    System.out.println(getOptimalString("1100"));
    }
//From input "1100" the expected result should "0101" but I get "0011"...