【Leetcode】131.分割回文串

输入: "aab"
输出:
[
  ["aa","b"],
  ["a","a","b"]
]

class Solution {
    public List<List<String>> partition(String s) {
        List<List<String>> res = new LinkedList<>();
        if (s == null || s.length() == 0) { return res;}
        List<String> current = new LinkedList<>();
        helper(res, current, s, 0);
        return res;
    }

    public void helper(List<List<String>> res, List<String> current, String s, int startIndex) {
        if (s.length() == startIndex) {
            res.add(new LinkedList<>(current));
            return;
        }

        for (int i = startIndex; i < s.length(); i++) {
            String currentPartition = s.substring(startIndex, i + 1);
            if (currentPartition.isEmpty() || !isPalindrome(currentPartition)) {
                continue;
            }
            current.add(currentPartition);
            helper(res, current, s, i+1);
            current.remove(current.size() - 1);
        }
    }

    public boolean isPalindrome(String s) {
        char[] res = s.toCharArray();
        int left = 0;
        int right = s.length() - 1;
        while (left <= right) {
            if (res[left] !=res[right]) {
                return false;
            }
            left++;
            right--;
        }
        return true;
    }
}