Problem

Spotify tracks user activity strings where each character represents an event type. Given a string s, return the length of the longest substring without repeating characters.

A substring is a contiguous sequence of characters within the string. You must design an algorithm better than checking all possible substrings.

Formal Specification

• Input: a string s
• Output: an integer representing the maximum length of a substring of s that contains no duplicate 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 with more than one character contains a repeated "b", so the best answer is 1.

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) <= 5 * 10^4
• s consists of English letters, digits, symbols, and spaces
• Return only the maximum length, not the substring itself