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.

Example:

Given s = "aab", return:

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

Solution:

Similar to Subsets problem. We could use depth first search to solve it.

Code:

public class Solution {

    public List<List<String>> partition(String s) {
        List<List<String>> res = new ArrayList<>();
        if (s == null || s.length() == 0) {
            return res;
        }
        List<String> path = new ArrayList<>();
        char[] chars = s.toCharArray();
        partitionHelper(chars, 0, path, res);
        return res;
    }

    private void partitionHelper(char[] chars, int index, List<String> path,
                    List<List<String>> res) {
        if (index >= chars.length) {
            res.add(new ArrayList<>(path));
        }
        StringBuilder sb = new StringBuilder();
        for (int i = index; i < chars.length; i++) {
            sb.append(chars[i]);
            if (isPalindrome(chars, index, i)) {
                path.add(sb.toString());
                partitionHelper(chars, i + 1, path, res);
                path.remove(path.size() - 1);
            }
        }
    }

    private boolean isPalindrome(char[] chars, int start, int end) {
        while (start < end) {
            if (chars[start] != chars[end]) {
                return false;
            }
            start++;
            end--;
        }
        return true;
    }
}