Sliding Window on string
Last updated: May 22, 2026
Quick Overview
Given a string, implement a sliding window algorithm to find the length of the longest substring without repeating characters. The function should take a string as input and return an integer representing the length of the longest substring that meets the criteria.
Meta
May 22, 2026111
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3,215 solved
Given a string, implement a sliding window algorithm to find the length of the longest substring without repeating characters. The function should take a string as input and return an integer representing the length of the longest substring that meets the criteria.
This coding problem is frequently asked during Onsite at Meta. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Meta expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Recognize the underlying problem pattern (sliding window, two pointers, BFS/DFS, etc.)
- Discuss multiple approaches and trade-offs before coding
- Implement an optimal solution with clean, production-quality code
- Handle all edge cases including boundary conditions and invalid input
- Optimize both time and space complexity with clear justification
- Test your solution systematically with well-chosen examples
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- How would you parallelize this solution?
- How would your solution change if the input was sorted?
- What happens if the input contains duplicates?
- Can you optimize the space complexity of your solution?
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Problem Analysis
The problem requires us to find the length of the longest substring without repeating characters in a given string. This problem can be effectively solved using the sliding window technique, which is ...
Approach
- Initialize two pointers,
startandend, both set to 0. These pointers will define the current substring window. - Use a set to track characters currently in the window. This will help quickly ...
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