Number of Good Ways to Split a String

You are given a string s. A split is considered good if you can divide s into two non-empty strings s_left and s_right such that their concatenation equals s, and the number of distinct characters in s_left and s_right is the same. Return the number of good splits you can make in s.

Constraints

• 1 <= s.length <= 10^5
• s consists of only lowercase English letters.