2262. Total Appeal of A String

The appeal of a string is the number of distinct characters found in the string. - For example, the appeal of "abbca" is 3 because it has 3 distinct characters: 'a', 'b', and 'c'. Given a string s, return the total appeal of all of its substrings. A substring is a contiguous sequence of characters within a string. Example 1: Input: s = "abbca" Output: 28 Explanation: The following are the s