Problem

In Meta Messenger, you are given a string s representing a message. Return the length of the longest substring that contains no repeated characters.

A substring must be contiguous. You should solve this efficiently for large inputs.

Formal Specification

• Input: A string s
• Output: An integer representing the maximum length of a substring of s with all unique characters

Examples

Example 1

• Input: s = "abcabcbb"
• Output: 3
• Explanation: The longest substring without repeating characters is "abc", which has length 3.

Example 2

• Input: s = "bbbbb"
• Output: 1
• Explanation: Every substring longer than length 1 repeats the character "b".

Example 3

• Input: s = "pwwkew"
• Output: 3
• Explanation: One valid longest substring is "wke". "pwke" is not valid because it is not contiguous.

Constraints

• 0 <= len(s) <= 10^5
• s may contain letters, digits, symbols, and spaces
• Return only the maximum length, not the substring itself