Detect permutation in array
Last updated: July 8, 2025
Quick Overview
Given array, detect all occurrences of the anagram pattern.
Robinhood
Coding & Algorithms
Software Engineer
Robinhood
July 8, 2025Software Engineer
Technical Screen
Coding & Algorithms
Medium
8
12
2,601 solved
Given array, detect all occurrences of the anagram pattern.
Robinhood 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
- 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
Dynamic programming and memoization
Edge cases and input validation
Common algorithm patterns (sliding window, two pointers, BFS/DFS)
Hash maps and frequency counting
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 test this solution thoroughly?
- What is the worst-case input for your solution?
- Can you solve this in a single pass?
- How would your solution change if the input was sorted?
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Practice DSA ProblemsSample Answer
Problem Analysis
To detect all occurrences of an anagram pattern in a given array, we can recognize that this problem can be tackled using the sliding window technique combined with frequency counting. The sli...
Approach
- Initialize Variables: Create two frequency count dictionaries: one for the anagram pattern (
pattern_count) and another for the current window in the array (window_count). Initialize the siz...
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