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This is a Medium difficulty Coding & Algorithms question, commonly asked during Onsite rounds at Amazon.

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This question is commonly asked for Data Scientist candidates at Amazon during technical interviews.

Implement Python Function for Longest Unique Substring Length | Amazon Interview Question

Implement Python Function for Longest Unique Substring Length

Last updated: Mar 29, 2026

Quick Overview

This question evaluates string manipulation and algorithmic problem-solving skills by requiring a Python implementation to determine the length of the longest substring without repeating characters, with an optional follow-up to extract all maximal substrings.

Amazon

Aug 4, 2025, 10:55 AM

Data Scientist

Onsite

Coding & Algorithms

Scenario

Real-time text analytics service enforcing uniqueness constraints

Question

Implement a Python function returning the length of the longest substring without repeating characters. Follow-up: modify it to return all substrings that meet this criterion.

Hints

Sliding window with hash map for indices; for follow-up, track start positions and collect substrings of max length.

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