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NVIDIA·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Apr 2026

Summary

NVIDIA software engineer interview with a data processing problem that looked straightforward until I actually had to think about the aggregation logic under the hood.

Questions Asked (1)

Q1

Given a list of log entries where each entry has an HTTP status code and a response time, aggregate the data by status code and return the count and average response time for each code.

Algorithms & Data StructuresAPI & Integrations
Author's notes

Went with a single-pass approach using a hashmap to accumulate totals and counts, then computed averages at the end.

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AI HintsAI Generated

Suggested Approach

Clarify the input format and constraints, then propose a single-pass hash map solution that accumulates count and sum of response times per status code. After processing, compute averages and return the aggregated results, discussing time and space complexity.

Pro tip: Mention that you would use a dictionary keyed by status code and store both count and sum to avoid storing all response times, which is memory efficient for large logs. Also, discuss handling edge cases like empty input or non-integer response times.

1. Clarify requirements and constraints

Ask about the input format (e.g., list of objects, arrays), data types, expected size, and whether response times are integers or floats. Confirm output format (e.g., dictionary mapping status code to {count, average}).

2. Choose data structures

Use a hash map (dictionary) where each key is a status code and the value is a pair (count, sum of response times). This allows O(1) updates per entry.

3. Iterate and aggregate

Loop through each log entry, extract status code and response time, and update the corresponding count and sum in the hash map. Handle missing keys by initializing count=0 and sum=0.

4. Compute averages and format output

After processing all entries, iterate over the hash map to compute average = sum / count for each status code. Return a new structure with count and average (rounded if necessary).

5. Analyze complexity and edge cases

State time complexity O(n) and space complexity O(k) where k is number of unique status codes. Discuss edge cases: empty input, single entry, division by zero (none since count>0), and potential integer overflow for large sums.

Key Points to Mention

  • Use a hash map to aggregate counts and sums in a single pass.
  • Avoid storing all response times; only keep running sum and count.
  • Time complexity O(n), space complexity O(k) for k unique status codes.
  • Handle edge cases: empty input, missing keys, and large numbers.
  • Consider rounding or formatting of average response time.
  • Discuss potential parallelization or streaming for very large logs.

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