public class DayCode {    public static void main(String[] args) {        String s = "aab";        List ans = new DayCode().partition(s);        System.out.println("ans is " + ans.toString());    }
    /**     * https://leetcode-cn.com/problems/palindrome-partitioning/     * @param s     * @return     */    public List<List<String>> partition(String s) {        List<List<String>> ans = new ArrayList<>();        int len = s.length();        if (len == 0) {            return ans;        }
        Deque<String> stack = new ArrayDeque<>();        char[] charArray = s.toCharArray();        dfs(charArray, 0, len, stack, ans);
        return ans;    }
    /**     * 子串     *     * @param charArray     * @param index     * @param len     * @param path     * @param ans     */    private void dfs(char[] charArray, int index, int len, Deque<String> path, List<List<String>> ans) {        if (index == len) {            ans.add(new ArrayList<>(path));            return;        }
        for (int i = index; i < len; i++) {            if (!checkPalindrome(charArray, index, i)) {                continue;            }            path.addLast(new String(charArray, index, i + 1 - index));            dfs(charArray, i + 1, len, path, ans);            path.removeLast();        }    }
    /**     * 验证回文串     *     * @param charArray     * @param left     * @param right     * @return     */    private boolean checkPalindrome(char[] charArray, int left, int right) {        while (left < right) {            if (charArray[left] != charArray[right]) {                return false;            }            left++;            right--;        }        return true;    }}