Given a string
s, return the length of the longest substring between two equal characters, excluding the two characters. If there is no such substring return
A substring is a contiguous sequence of characters within a string.
Input: s = "aa" Output: 0 Explanation: The optimal substring here is an empty substring between the two
Input: s = "abca" Output: 2 Explanation: The optimal substring here is "bc".
Input: s = "cbzxy" Output: -1 Explanation: There are no characters that appear twice in s.
Input: s = "cabbac" Output: 4 Explanation: The optimal substring here is "abba". Other non-optimal substrings include "bb" and "".
1 <= s.length <= 300
scontains only lowercase English letters.