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Capital One·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Apr 2026

Summary

Capital One software engineer round with one meaty simulation problem. Not a typical LeetCode grind, more like a logic puzzle dressed up as a real-world scenario, which I wasn't expecting.

Questions Asked (1)

Q1

Given a list of integers representing each person's arrival time at a food queue, simulate the check-in process where each person at the front takes 30 seconds to check in and anyone who arrives when the queue has more than 10 people leaves without checking in. Return each person's check-in time, or null if they left.

Algorithms & Data StructuresSystem Design
Author's notes

The problem reads like a wall of text and my first instinct was to skim it, which was a mistake.

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AI HintsAI Generated

Suggested Approach

Clarify the problem constraints and edge cases, then propose a simulation using a queue data structure that tracks arrival times and check-in times. Walk through a small example to validate the logic, and discuss time and space complexity.

Pro tip: Explicitly handle the case where multiple people arrive at the same time and the queue length threshold is exceeded, as this is a common edge case that can trip up candidates.

1. Clarify Requirements

Ask questions to confirm details: Are arrival times sorted? What is the exact queue length threshold (more than 10)? Does the person who arrives when the queue is too long leave immediately, or do they wait? What is the output format?

2. Choose Data Structures

Use a queue to simulate the line, storing each person's arrival time and index. Track the current time and the queue length to determine when someone leaves.

3. Simulate the Process

Iterate through arrivals in order. For each person, first process check-ins that occur before their arrival time. If the queue length exceeds 10 at arrival, mark them as null; otherwise, add them to the queue.

4. Compute Check-in Times

After all arrivals, process remaining people in the queue. Each check-in takes 30 seconds, so the check-in time is the current time plus 30 seconds per person.

5. Analyze Complexity

State that the time complexity is O(n) since each person is processed once, and space complexity is O(n) for the queue and output array.

Key Points to Mention

  • Use of a queue to simulate the line and track order.
  • Handling simultaneous arrivals and the queue length threshold correctly.
  • Time complexity analysis: O(n) time and O(n) space.
  • Edge cases: empty input, all leave, no one leaves, large gaps between arrivals.
  • Clarifying assumptions with the interviewer before coding.
  • Testing with a small example to verify logic.

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