Longest substring between two identical characters of leetcode simple question

subject

Give you a string s, Please return The length of the longest substring between two identical characters , The length is calculated without these two characters . If there is no such substring , return -1 .
Substring Is a sequence of consecutive characters in a string .
Example 1：
Input ：s = “aa”
Output ：0
explain ： The optimal substring is two ‘a’ Empty substring between .
Example 2：
Input ：s = “abca”
Output ：2
explain ： The optimal substring is “bc” .
Example 3：
Input ：s = “cbzxy”
Output ：-1
explain ：s There is no character that appears twice in , So back -1 .
Example 4：
Input ：s = “cabbac”
Output ：4
explain ： The optimal substring is “abba” , Other non optimal solutions include “bb” and “” .
Tips ：
1 <= s.length <= 300
s Only lowercase English letters
source ： Power button （LeetCode）

Their thinking

   This problem can start with the character frequency . Count the frequency of characters , If the frequency is greater than or equal to 2, It means that , There may be a substring in the middle of this character ; If the frequency is exactly equal to 2, Then the generated string is only one , If exceeded 2 Then there will be multiple strings , But the longest string is the string between the first occurrence and the last occurrence , So we can start from both ends to search for the position of the same character , And calculate the length of the current longest string .

class Solution:
    def maxLengthBetweenEqualCharacters(self, s: str) -> int:
        freq=Counter(s)
        MAX=-1
        for i,j in freq.items():
            if j>1:
                left=s.index(i)  # First occurrence 
                right=len(s)-s[::-1].index(i)-1# The last location 
                if right-left-1>MAX: # Maximum string length update 
                    MAX=right-left-1
        return MAX