159. Longest Substring with At Most Two Distinct Characters

Given a string s , find the length of the longest substring  t   that contains at most 2 distinct characters.

Example 1:

Input:

 "eceba"
Output: 

3
Explanation: 
t


 

is "ece" which its length is 3.

Example 2:

Input:

 "ccaabbb"
Output: 

5
Explanation: 
t


 

is "aabbb" which its length is 5.