Let T be a text string of length n and let S be a list of m characters ( characters may repeat). Give an O(n) algorithm to find all the substrings in T that can be formed by using all the characters in S. Note that all such substrings must be of size m. For example S=[a, a, b, c] and T=abahgcabah.Then 'caba' is the only substring of T that can be from all the characters in S. (probably using suffix tree, but I got confused if i can actually achieve O(n))