A solution to the problem to find if a String is an anagram of a Palindrome

AnagramPalindrome

    // In order to know if a String or char[] is an anagram of a palindrome we look up to the 
    // math definition of a palindrome: There must be an even number of every char except for the
    // case there is a single letter in the middle, in which case we can afford only 1 instance of
    // an odd character in the middle.
    public boolean solution(char[] input) {
        int[] letters = new int[26];

        // We calculate frequencies to each of the letters
        for (int i = 0; i < input.length; i++) {
            // We lowercase the chars and compensate for the UTF-8 displacement to the right
            letters[Character.getNumericValue(Character.toLowerCase(input[i])) - 10]++;
        }

        // Counting odd characters.
        int oddCounter = 0;
        for (int i = 0; i < letters.length; i++) {
            if (letters[i] % 2 != 0) {
                oddCounter++;
            }
        }
        // O(n+26) still accounts for O(n) :P
        return oddCounter <= 1;
    }