Optimize compression for O(1) space
Last updated: May 25, 2026
Quick Overview
Design an algorithm to optimize the compression of a given string such that it uses O(1) space. The input will be a string consisting of lowercase letters, and the output should be the compressed version of the string, where consecutive duplicates are represented by the character followed by the count of its occurrences. Ensure that the solution does not use any additional data structures that grow with input size.
Confluent
May 25, 202633
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Design an algorithm to optimize the compression of a given string such that it uses O(1) space. The input will be a string consisting of lowercase letters, and the output should be the compressed version of the string, where consecutive duplicates are represented by the character followed by the count of its occurrences. Ensure that the solution does not use any additional data structures that grow with input size.
This coding problem is frequently asked during Technical Screen at Confluent. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Confluent 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 modify your solution to handle streaming input?
- What is the worst-case input for your solution?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to compress a string of lowercase letters by representing consecutive duplicates with the character followed by the count of its occurrences. The key constraint is that we need...
Approach
The algorithm can be outlined as follows:
- Initialize a pointer
ito iterate through the string and a variablecountto track the occurrences of the current character. - Use another pointer to ...
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