132. 分割回文串 II

输入: "aab"
输出: 1
解释: 进行一次分割就可将 s 分割成 ["aa","b"] 这样两个回文子串。

class Solution {
    
    int min = Integer.MAX_VALUE;
    
    private boolean isPalin(String s) {
        int start = 0;
        int end = s.length() - 1;
        while (start < end) {
            if (s.charAt(start) != s.charAt(end)) {
                return false;
            }
            start++;
            end--;
        }
        return true;
    }

    public int minCut(String s) {
        List<String> list = new ArrayList<>();
        helper2(list, s, 0);
        return min;
    }

    private void helper2(List<String> list, String s, int start) {
        if (start == s.length()) {
            min = Math.min(min, list.size() - 1);
            return;
        }
        for (int i = start; i < s.length(); i++) {
            String sub = s.substring(start, i + 1);
            if (isPalin(sub)) {
                list.add(sub);
                helper2(list, s, i + 1);
                list.remove(list.size() - 1);
            }
        }
    }
}