Sliding Window on string
Last updated: February 16, 2026
Quick Overview
Given a string, implement the Sliding Window algorithm to find the length of the longest substring without repeating characters. Your function should take a single string as input and return an integer representing the length of the longest substring.
Atlassian
February 16, 202614
15
4,510 solved
Given a string, implement the Sliding Window algorithm to find the length of the longest substring without repeating characters. Your function should take a single string as input and return an integer representing the length of the longest substring.
This coding problem is frequently asked during Take-home Project at Atlassian. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Atlassian expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
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
- What happens if the input contains duplicates?
- What if the input doesn't fit in memory?
- How would you modify your solution to handle streaming input?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Problem Analysis
The problem requires us to find the length of the longest substring without repeating characters from a given string. The sliding window technique is optimal here because it allows us to dynamically a...
Approach
- Initialize two pointers,
leftandright, to represent the current window of characters. Start both at the beginning of the string. - Use a dictionary to track characters and their latest ind...
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