Palindrome Partitioning

Given a string s, partition s such that every substring of the partition is a palindrome.

Return all possible palindrome partitioning of s.

For example, given s = "aab",
Return

  [
    ["aa","b"],
    ["a","a","b"]
  ]

Solution:
DFS transformation.
Hints: return all possible ... For "all" questions, it typically relates to DFS.

public class Solution {
    public ArrayList> partition(String s) {
        ArrayList> result = new ArrayList>();
        ArrayList subset = new ArrayList();
        helper(s, 0, result, subset);
        return result;
    }
    
    public void helper(String s, int begin, ArrayList> result, ArrayList subset){
        if(begin == s.length()){
            result.add(new ArrayList(subset));
            return;
        }
        for(int i = begin; i < s.length(); i++){
            String str = s.substring(begin, i+1);
            if (isPalindrome(str)){
                subset.add(str);
                helper(s, i+1, result, subset);
                subset.remove(subset.size()-1);
            }
        }
    }
    
    public boolean isPalindrome(String str){
        int l = 0;
        int r = str.length() - 1;
        while(l < r){
            if(str.charAt(l) != str.charAt(r))
                return false;
            l++;
            r--;
        }
        return true;
    }
}