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Prefix Lookup Service for a Word Dictionary
Given a dictionary of words, build a structure that can efficiently count how many dictionary words start with a given prefix.
1. Problem Statement
Design a structure that supports inserting integers one at a time from a stream and returning the median of all values inserted so far, at any point.
2. Live Coding Format
Work in the provided coding workspace while explaining your decisions to the live interviewer. Validation may use inline tests, examples, comments, or a verbal walkthrough.
3. Key Focus Areas
- 1Problem clarification and contract
- 2Approach exploration and optimality
- 3Think-aloud communication and pacing
- 4Implementation correctness
- 5Code quality and language fluency
- 6Handwritten tests and dry run
- 7Debugging and self-correction
- 8Complexity analysis
- 9Follow-up performance
4. What Strong Candidates Should Demonstrate
- ✓Clarify insertion frequency, query frequency, and duplicate/negative value assumptions before coding.
- ✓Explain a naive sorted-storage baseline and improve to a balanced two-heap design.
- ✓Think aloud while implementing careful heap balancing logic.
- ✓Validate with explicit expected outputs and a top-to-bottom handwritten dry run.
- ✓Analyze time and space complexity and handle a focused follow-up extension.
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Practice this problem in the live coding workspace while the interviewer probes your clarification, implementation, trade-offs, and validation.
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HeapsStreamingData Structure DesignComplexity Analysis
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