Find longest substring without repeating characters

Q: Find longest substring without repeating characters

This is a Coding & Algorithms interview question from ByteDance for Machine Learning Engineer roles. View the full question and solution on PracHub.

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Question

Problem

Given a string s, find the length of the longest contiguous substring that contains no repeated characters.

Input

A string s (may contain letters, digits, symbols, and spaces).

Output

An integer: the maximum length among all substrings of s that have all unique characters.

Examples

s = "abcabcbb" → output 3 (e.g., "abc")
s = "bbbbb" → output 1 (e.g., "b")
s = "pwwkew" → output 3 (e.g., "wke")

Constraints (typical interview assumptions)

0 ≤ len(s) ≤ 10^5
Aim for an algorithm faster than O(n^2) .

Notes

Substring must be contiguous (not a subsequence).