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Waymo·Software Engineer·Technical Phone Screen·Intermediate

IntermediateRejected
Apr 2026

Summary

Waymo SWE interview that didn't go great. Got a LeetCode problem I'd never seen before and it turned out to hinge on bucket sort, which I hadn't really prepped for.

Questions Asked (1)

Q1

Solve a LeetCode problem that requires bucket sort as the key algorithmic technique.

Algorithms & Data Structures
Author's notes

I fumbled through it.

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AI HintsAI Generated

Suggested Approach

First, clarify the problem requirements and constraints, then identify if the data can be bucketed by a key (e.g., value range, frequency, or digit). Explain why bucket sort is optimal (e.g., O(n) time when buckets are balanced) and outline the steps: create buckets, distribute elements, sort within buckets if needed, and concatenate. Finally, discuss trade-offs and edge cases.

Pro tip: Mention that bucket sort is stable and can be adapted for distributed systems, which is relevant for large-scale data processing at Waymo. Also, proactively discuss how to handle skewed data by choosing bucket boundaries wisely or using a hybrid approach.

1. Understand the problem and constraints

Restate the problem in your own words, ask clarifying questions about input size, value range, and expected output. Identify if the data has a natural bucketing key (e.g., numeric range, frequency, or digit).

2. Choose bucket sort and justify

Explain why bucket sort is suitable: it can achieve O(n) average time when data is uniformly distributed. Compare with other sorting algorithms (e.g., quick sort, counting sort) and highlight trade-offs.

3. Design the bucketing scheme

Define how to map elements to buckets (e.g., value ranges, hash function). Decide the number of buckets and how to handle collisions or uneven distribution. Consider if buckets need to be sorted individually.

4. Implement and walk through an example

Write pseudocode or actual code, explaining each step. Trace through a small example to demonstrate correctness, including edge cases like empty input or all elements in one bucket.

5. Analyze complexity and discuss optimizations

State time and space complexity: O(n + k) average, O(n^2) worst-case if buckets are unbalanced. Discuss optimizations like using insertion sort for small buckets or dynamic bucket sizing.

Key Points to Mention

  • Time complexity: average O(n + k), worst-case O(n^2) when all elements fall into one bucket.
  • Space complexity: O(n + k) for buckets and auxiliary arrays.
  • Stability: bucket sort is stable if the underlying sort is stable.
  • Choice of bucket boundaries: uniform distribution assumption; can use value range or hash function.
  • Handling skewed data: use dynamic bucket sizing or hybrid approach with comparison sort.
  • Real-world applications: distributed sorting, external sorting, and scenarios with known value ranges.

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