Problem

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

This is a standard string and sliding-window problem: scan the string once and maintain the largest valid window with all unique characters.

Formal Specification

• Input: a string s
• Output: an integer representing the maximum length of a substring of s with all distinct 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 answer is "wke". "pwke" is not valid because a substring must be contiguous.

Constraints

• 0 <= len(s) <= 5 * 10^4
• s contains English letters, digits, symbols, and spaces
• Your solution should run in linear time