Longest Consecutive Duplicate String

Hello !, I am a participant of hacktober fest 2021 , I would like to add this important question regarding strings.

Problem statement: Given a lowercase alphabet string s, return the length of the longest substring with same characters.

Constraints:
0<=n<=100000 , where n is length of string s.
Example cases:

Example 1:
s = "abbbba"
Output: 4
Explanation: The longest substring is "bbbb".

Example 2:
s = "aaabbb"
Output: 3
Explanation: The longest substring is either 'aaa' or 'bbb'.

Please assign me this issuse.