A string X is an anagram of string Y if X can be obtained by arranging all characters of Y in some order, without removing any characters and without adding new characters. For example, each of the strings "baba", "abab", "aabb" and "abba" is an anagram of "aabb", and strings "aaab", "aab" and "aabc" are not anagrams of "aabb".
A set of strings is anagram-free if it contains no pair of strings which are anagrams of each other. Given a set of strings S, return the size of its largest anagram-free subset. Note that the entire set is considered a subset of itself.