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Cheapest Route Within a Stop Limit
Given one-way routes between cities each with a cost, find the cheapest total cost from a source city to a destination city using at most k intermediate stops.
1. Problem Statement
You are given a number of courses labeled 0 to n-1 and a list of prerequisite pairs [course, prereq] meaning prereq must be completed before course. Return a valid order to complete all courses, or an empty list if it is impossible.
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 prerequisite direction, duplicate edges, and impossible-order behavior before coding.
- ✓Explain a naive repeated-scan baseline and improve to Kahn's algorithm or DFS-based topological sort.
- ✓Think aloud while implementing careful graph traversal and cycle detection.
- ✓Validate with explicit expected outputs and a top-to-bottom handwritten dry run.
- ✓Analyze time and space complexity and handle a bounded follow-up modification.
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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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GraphsTopological SortCycle DetectionComplexity Analysis
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Fewest Moves to Solve a Sliding Tile Puzzle
Given a small 2-by-3 sliding tile puzzle board with one blank space, find the minimum number of adjacent tile slides needed to reach a specified target arrangement, or report it is unreachable.
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Track Connectivity Across a Growing Network
Given a number of servers and a sequence of direct connection events between pairs of servers, answer whether two given servers are connected after each event, processing many union and query operations efficiently.
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Count Connected Land Regions in a Grid
Given a 2D grid of land and water cells, count the number of distinct connected land regions, where cells are connected horizontally or vertically.