Problem
Given a string s, find the length of the longest substring without duplicate characters.
Examples
Example 1:
Input: s = “abcabcbb”
Output: 3
Explanation: The answer is “abc”, with the length of 3. Note that "bca" and "cab" are also correct answers.Example 2:
Input: s = “bbbbb”
Output: 1
Explanation: The answer is “b”, with the length of 1.Example 3:
Input: s = “pwwkew”
Output: 3
Explanation: The answer is “wke”, with the length of 3.
Notice that the answer must be a substring, “pwke” is a subsequence and not a substring.Constraints
0 <= s.length <= 5 * 10^4sconsists of English letters, digits, symbols and spaces.
How to participate
Drop your solution as a comment (or link a gist) by April 30, 2026 at noon Pacific Time.
Include:
Your programming language
Brief explanation of your approach
Stated complexity
What I’ll do
By May 2, I’ll publish a Review & Lessons post with:
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A clean reference solution
Notes on how an interviewer would evaluate your approach.
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