Longest Substring with At Most Two Distinct Characters

Given a string s, return the length of the longest substring that contains at most two distinct characters.

Examples

Example 1:

Input: s = "eceba"

Output: 3

Explanation: The substring "ece" has length 3 with two distinct characters ('e' and 'c').

Example 2:

Input: s = "ccaabbb"

Output: 5

Explanation: The substring "aabbb" has length 5 with two distinct characters ('a' and 'b').

Example 3:

Input: s = "a"

Output: 1

Explanation: The entire string has only one distinct character.

Constraints

• 1 <= s.length <= 10⁵
• s consists of English letters.