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Datadog·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Datadog software engineer interview with a coding question about bucketing sorted integers. Pretty straightforward problem but there are a couple of edge cases worth thinking through.

Questions Asked (1)

Q1

Given a sorted array of integers, a bucket width, and a number of buckets, distribute the values into buckets and return the count per bucket. The last bucket is a catch-all for anything that overflows the regular range.

Algorithms & Data Structures
Author's notes

The core logic is pretty clean once you see it: for each value just do integer division by the bucket width and clamp to the last bucket index.

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AI HintsAI Generated

Suggested Approach

Clarify the bucket boundaries and overflow handling, then design a single-pass algorithm that computes each element's bucket index in O(1) time. Handle edge cases like negative numbers, values below the first bucket, and values exceeding the regular range, ensuring the last bucket catches all overflow.

Pro tip: Explicitly discuss how to handle negative values and values below the first bucket, as many candidates forget that the first bucket may also need a catch-all for underflow. Also, mention that the algorithm should be O(n) time and O(1) extra space (besides the output array).

1. Clarify requirements and edge cases

Ask about bucket boundaries, whether buckets are inclusive/exclusive, how negative numbers and values below the first bucket are handled, and confirm the overflow behavior for the last bucket.

2. Define bucket index formula

Derive a formula to map a value to its bucket index, e.g., index = (value - min_value) / bucket_width, with adjustments for negative values and clamping to the last bucket for overflow.

3. Design the algorithm

Iterate through the sorted array once, compute the bucket index for each element, and increment the corresponding count. Use the sorted property to potentially early-exit or optimize if needed.

4. Handle overflow and underflow

Ensure that values exceeding the regular range are placed in the last bucket, and consider if a similar catch-all is needed for values below the first bucket (e.g., if negative values are allowed).

5. Analyze complexity and test

State that the time complexity is O(n) and space complexity is O(k) for the output. Walk through examples, including edge cases like empty array, all elements in one bucket, and overflow.

Key Points to Mention

  • Bucket index calculation: (value - min) / width, with integer division and handling of negative numbers.
  • Overflow handling: values >= min + width * (num_buckets - 1) go into the last bucket.
  • Underflow handling: if negative values are possible, decide whether the first bucket is a catch-all for values below the range.
  • Time complexity: O(n) single pass; space complexity: O(k) for the result array.
  • Edge cases: empty array, all values in one bucket, values exactly on boundaries, and large numbers causing overflow in index calculation.
  • Use of sorted property: can early-exit if remaining values are all in the last bucket, but not necessary for O(n).

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