Flip Game II

public class Solution {
    public boolean canWin(String s) {
        if (s.length() < 2) {
            return false;
        }
        List<String> result = new ArrayList<>();
        for (int i = 0; i < s.length() - 1; i++) {
            if (s.charAt(i) == '+' && s.charAt(i+1) == '+') {
                result.add(s.substring(0, i) + "--" + s.substring(i+2));
            }
        }
        for (String next : result) {
            if (!canWin(next)) {
                return true;
            }
        }
        return false;
    }
}