public class Solution {
    /**
     * @param s: A string
     * @return: A list of lists of string
     */
    public List<List<String>> partition(String s) {
        // write your code here
        List<List<String>> result = new ArrayList<>();
        if (s == null || s.isEmpty()) {
            return result;
        }
        List<String> palindrome = new ArrayList<>();
        partitionHelper(s, 0, result, palindrome);
        return result;
    }

    public void partitionHelper(String s, int pos, List<List<String>> result, List<String> palindrome){
        if (s.length() == pos) {
            result.add(new ArrayList<String>(palindrome));
            return;
        }

        for (int i = pos + 1; i <= s.length(); i++) {
            String temp = s.substring(pos, i);
            if (!isPalindrome(temp)) {
                continue;
            }
            palindrome.add(temp);
            partitionHelper(s, i, result, palindrome);
            palindrome.remove(palindrome.size() - 1);
        }
    }

    public boolean isPalindrome(String words) {
        if (words == null || words.isEmpty()) {
            return false;
        }
        int length = words.length();
        for (int i = 0; i < length - i; i++) {
            if (words.charAt(i) != words.charAt(length - i - 1)) {
                return false;
            }
        }
        return true;
    }
}