Greedy on string
Last updated: May 14, 2026
Quick Overview
Given a string consisting of lowercase letters, your task is to rearrange the characters in such a way that no two adjacent characters are the same. Implement a function that returns the rearranged string if possible, or an empty string if it is not feasible. The function should handle edge cases and ensure optimal performance, adhering to a greedy algorithm approach.
Elastic
May 14, 202631
13
2,575 solved
Given a string consisting of lowercase letters, your task is to rearrange the characters in such a way that no two adjacent characters are the same. Implement a function that returns the rearranged string if possible, or an empty string if it is not feasible. The function should handle edge cases and ensure optimal performance, adhering to a greedy algorithm approach.
Elastic uses this problem in the Technical Screen to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
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
- Can you solve this iteratively instead of recursively (or vice versa)?
- How would you test this solution thoroughly?
- What is the worst-case input for your solution?
- How would you modify your solution to handle streaming input?
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Practice DSA ProblemsSample Answer
Problem Analysis
To solve the problem of rearranging characters in a string such that no two adjacent characters are the same, we can recognize that this is a greedy algorithm problem. The primary pattern we can apply...
Approach
- Count Character Frequencies: Use a frequency counter (like a dictionary) to count how many times each character appears in the string.
- Max-Heap Creation: Insert all characters into a max...
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