Let T be a text string of length m and let S be a multiset of n characters. The problem is to find all substrings in T of length n that are formed by the characters of S. For example, let S = (a, a, b, c} and T = abahgcabah. Then caba is a substring of T formed from the characters of S. Give a solution to this problem that runs in O(m) time. The method should also be able to state, for each position i, the length of the longest substring in T starting at i that can be formed from S.