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Amazon·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say
Apr 2026

Summary

Amazon SWE coding round with one algorithmic problem. Spent too long going down the wrong path and only figured out the cleaner solution after the fact.

Questions Asked (1)

Q1

Given a set of branches being merged, find the minimum number of commit conflicts that result. What's the most efficient approach?

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

My first instinct was backtracking through permutations and counting conflicts for each ordering.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem: define what a 'commit conflict' means (e.g., same file modified in different branches) and the merge model (e.g., merging all branches into one). Then propose modeling the branches and their commits as a graph or interval overlap problem, and discuss algorithms like greedy interval scheduling or union-find to minimize conflicts. Finally, analyze time/space complexity and trade-offs between different approaches.

Pro tip: Amazon values customer obsession and ownership; relate the problem to real-world scenarios like reducing merge conflicts in CI/CD pipelines, and mention how you'd validate the solution with unit tests and edge cases.

1. Clarify the problem

Ask questions to understand the definition of a conflict, the merge strategy (e.g., sequential vs. simultaneous), and constraints (number of branches, commits per branch).

2. Model the problem

Represent each branch as a set of commits (or files changed) and define conflicts as overlaps. Consider using intervals or graphs to capture relationships.

3. Propose an efficient algorithm

Suggest a greedy approach (e.g., sort by end time and select non-overlapping) or graph-based method (e.g., maximum independent set) to minimize conflicts, and justify its optimality.

4. Analyze complexity and trade-offs

Discuss time and space complexity, and compare with brute-force or other approaches. Mention scalability for large repositories.

5. Validate and test

Outline how to test the solution with edge cases (e.g., no conflicts, all conflicts) and potentially implement a prototype.

Key Points to Mention

  • Definition of commit conflict: overlapping changes in the same file or lines
  • Graph representation: branches as nodes, conflicts as edges
  • Greedy interval scheduling for minimizing conflicts
  • Union-Find for grouping non-conflicting branches
  • Time complexity: O(n log n) for sorting-based approaches
  • Trade-offs: accuracy vs. speed, and handling of transitive conflicts

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.