Reconstruct an Itinerary from Flight Tickets
Last updated: August 7, 2026
Quick Overview
Given a list of flight tickets represented as pairs of departure and arrival airports, reconstruct the itinerary in a way that uses all the tickets exactly once.
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Given a list of flight tickets represented as pairs of departure and arrival airports, reconstruct the itinerary in a way that uses all the tickets exactly once.
This question is often asked during onsite interviews for software engineering roles to evaluate a candidate's problem-solving skills and understanding of graph traversal algorithms. The interviewer is looking for the candidate's ability to think critically about how to represent the problem, choose the right algorithm, and implement a solution efficiently.
What the Interviewer Expects
- Clearly define the problem and constraints.
- Choose an appropriate data structure for the solution.
- Implement a depth-first search (DFS) or similar algorithm.
- Discuss the time and space complexity of the solution.
- Handle edge cases effectively.
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 optimize your solution for larger datasets?
- Can you explain how you would handle cycles in the graph?
- What would you do if the tickets could have multiple valid itineraries?
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Practice DSA ProblemsSample Answer
Approach
To solve the problem of reconstructing an itinerary from flight tickets, we can represent the flights as a directed graph where each airport is a node and each ticket is a directed edge from the depar...
Algorithm
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Build the Graph: Use a dictionary to map each departure airport to a list of arrival airports. Sort the arrival lists to ensure we visit airports in lexical order.
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DFS Traversal: Imple...
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