eBay Coding Interview Questions

Showing 8 problems of 25

• #1easyvery frequently asked

  1. Two Sum

  eBay phone screens frequently open with Two Sum as a warm-up to test hash-map fluency. In an e-commerce context, think of it as finding two item prices in a cart that sum to a target gift-card value — a dead-simple scenario that reveals whether you default to O(n²) brute force or reach for a hash map immediately.

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• #20easyfrequently asked

  20. Valid Parentheses

  eBay's backend services use expression parsers and template engines where bracket matching is foundational. This problem tests whether you can model state with a stack — a pattern that scales to validating JSON payloads, HTML templates, and complex search-query expressions used across eBay's marketplace platform.

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• #21easyfrequently asked

  21. Merge Two Sorted Lists

  eBay's search-ranking pipeline merges sorted result streams from multiple indices — the classic k-way merge problem reduces to this two-list base case. Interviewers use it to test pointer discipline and the dummy-node trick that eliminates edge-case conditionals. Mastering this sets you up for Merge K Sorted Lists in later rounds.

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• #53easyfrequently asked

  53. Maximum Subarray

  eBay's analytics teams compute rolling revenue windows — 'what was the best consecutive streak of profitable days this quarter?' Maximum Subarray (Kadane's algorithm) is the canonical solution. It's asked at eBay because it distinguishes candidates who memorize solutions from those who can derive the greedy insight on the spot.

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• #70easyfrequently asked

  70. Climbing Stairs

  eBay uses Climbing Stairs as a gentle DP entry point — it tests whether you can identify overlapping subproblems and avoid recomputation. Think of it as the number of ways to paginate through a search result: each page can advance 1 or 2 results at a time. Recognizing this as Fibonacci unlocks the O(1) space optimization that senior eBay engineers expect.

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• #121easyfrequently asked

  121. Best Time to Buy and Sell Stock

  eBay's marketplace handles dynamic pricing at enormous scale — think 'what is the maximum arbitrage on a collectible card across hourly price snapshots?' This classic single-pass problem is a direct analog, and eBay interviewers use it to test greedy thinking and whether you can reframe a min-prefix question without extra storage.

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• #206easyfrequently asked

  206. Reverse Linked List

  Linked list manipulation is a staple of eBay's entry-level interview loop. Think of it as reversing the order of items in a payment processing queue — a concrete scenario where pointer manipulation and in-place operations matter for memory efficiency at the scale of millions of concurrent transactions.

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• #217easysometimes asked

  217. Contains Duplicate

  eBay uses duplicate detection extensively — deduplicating search results, preventing double-listings, and fraud detection all rely on fast membership checks. Contains Duplicate is the simplest form of this pattern and tests whether you instinctively reach for a Set over a nested loop when you need O(n) duplicate detection.

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