난이도: Medium 문제 설명You are given two string arrays words1 and words2.A string b is a subset of string a if every letter in b occurs in a including multiplicity.For example, "wrr" is a subset of "warrior" but is not a subset of "world".A string a from words1 is universal if for every string b in words2, b is a subset of a.Return an array of all the universal strings in words1. You may return the an..