eBay Coding Interview Questions

Showing 9 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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• #3mediumvery frequently asked

  3. Longest Substring Without Repeating Characters

  eBay's search autocomplete and suggestion engine needs to deduplicate character sequences in query strings efficiently. This sliding-window problem is a medium staple in eBay's onsite loop because it requires coordinating a Set and two pointers to achieve O(n) — a clean test of sliding-window mastery before harder variants.

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• #4hardsometimes asked

  4. Median of Two Sorted Arrays

  eBay's pricing analytics team computes median transaction prices across two buyer segments in real time — combining sorted bid histories without merging them. Median of Two Sorted Arrays is the flagship O(log(m+n)) algorithm that eBay uses at the senior level to test binary search mastery beyond basic forms. The partition-based approach is notoriously tricky and strongly differentiates senior candidates.

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• #42hardsometimes asked

  42. Trapping Rain Water

  eBay's data visualization team renders capacity charts for warehouse storage — thinking of elevation bars as bin capacities and water as overflow volume. Trapping Rain Water is a classic two-pointer problem that eBay uses at the hard level to test whether candidates can optimize from O(n) space (prefix/suffix arrays) to O(1) space (two-pointer) through clear reasoning.

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• #84hardsometimes asked

  84. Largest Rectangle in Histogram

  eBay's seller analytics dashboard visualizes listing activity as bar charts — finding the largest contiguous block of equal or taller listings tells analysts about peak sustained activity windows. Largest Rectangle in Histogram is a stack-based hard problem that eBay uses to test monotonic stack mastery, one of the most powerful patterns for range-query problems.

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• #127hardsometimes asked

  127. Word Ladder

  eBay's catalog team maps product category transitions — how many steps does it take to reclassify a listing from one category to a related one, changing only one attribute at a time? Word Ladder is a BFS shortest-path problem on an implicit graph that eBay uses to test graph construction, BFS level-tracking, and neighbor-generation efficiency.

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• #146mediumvery frequently asked

  146. LRU Cache

  eBay's product catalog and search-result caching rely on LRU eviction to keep hot listings in memory while purging stale ones. This design problem tests whether you can compose a hash map and doubly-linked list to achieve O(1) get and put — a real production data structure that eBay's infrastructure engineering teams implement and discuss in depth.

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• #200mediumvery frequently asked

  200. Number of Islands

  eBay's geo-search team segments geographic regions — think grouping contiguous postal codes into delivery zones. Number of Islands is the graph-traversal foundation: count connected components in a grid. eBay interviewers use it to test BFS vs. DFS choice, visited-state management, and whether you can handle a 2D graph without a separate visited matrix.

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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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