class Solution {
  // O(n) O(n)
    public boolean canPermutePalindrome(String s) {
        HashSet<Character> set = new HashSet<Character>();

        for (Character c : s.toCharArray()) {
            if (!set.add(c)) {
                set.remove(c);
            }
        }

        return set.size() < 2;
    }
}