Tutorial

What is ρ(s, t) equal to? For every character of s and every character of t there is a unique cyclic shift of t that superposes these characters (indeed, after 0, ..., n - 1 shifts the character in t occupies different positions, and one of them matches the one of the character of s); therefore, there exist n cyclic shifts of s and t that superpose these characters (the situation is symmetrical for every position of the character of s). It follows that the input in ρ from a single character t_i is equal to n × (the number of characters in s equal to t_i). Therefore, ρ(s, t) is maximal when every character of t occurs the maximal possible number of times in s. Simply count the number of occurences for every type of characters; the answer is Kⁿ, where K is the number of character types that occur in s most frequently. This is an O(n) solution