DoorDash Coding Interview Questions

Showing 8 problems of 32

• #31hardfoundational

  31. Sliding Window Maximum

  Return the maximum value in each sliding window of size k — Doordash uses this deque pattern in their real-time demand forecasting: finding peak order rates over every rolling k-minute window to trigger Dasher surge dispatch.

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• #32hardfoundational

  32. Median of Two Sorted Arrays

  Find the median of two sorted arrays in O(log(m+n)) — Doordash uses binary-search-on-sorted-partition thinking in their real-time delivery ETA percentile calculations that must run in microseconds across millions of rows.

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• #42hardcompany favorite

  42. Trapping Rain Water

  Given an elevation map, compute how much rainwater would be trapped. DoorDash uses this as a hard-end array problem — they want the two-pointer O(1) space optimization, not just the precomputed-max arrays version.

  3 free resourcesSolve →
• #127hardfrequently asked

  127. Word Ladder

  Find the shortest transformation sequence from beginWord to endWord, changing one letter at a time and using only words in the dictionary. DoorDash leans on this for the BFS-on-implicit-graph pattern — they want to see the wildcard-key optimization on the adjacency lookup.

  3 free resourcesSolve →
• #212hardfrequently asked

  212. Word Search II

  Given a board and a list of words, return all words that can be formed by traversing adjacent cells. DoorDash uses this as a Trie + DFS combination — they want the trie-traversal speedup that beats naive per-word DFS.

  3 free resourcesSolve →
• #218hardfrequently asked

  218. The Skyline Problem

  Given a list of buildings (left, right, height), return the skyline as key points. DoorDash uses this for senior infrastructure rounds — the sweep-line + max-heap pattern shows up in surge-pricing and capacity-window problems.

  3 free resourcesSolve →
• #857hardfrequently asked

  857. Minimum Cost to Hire K Workers

  Hire exactly k workers so that each is paid at least their min-wage AND in proportion to their quality. Minimize total cost. DoorDash uses this for senior backend rounds — the dispatch and pricing problems have the same shape.

  3 free resourcesSolve →
• #1192hardfrequently asked

  1192. Critical Connections in a Network

  Given an undirected graph, return all bridges — the edges whose removal disconnects the graph. DoorDash candidates report interviewers want Tarjan's bridge-finding algorithm by name, because a logistics network is exactly the kind of system where a single point of failure between zones matters; the question grades whether you can explain discovery times and low-link values, not whether you memorized the code.

  3 free resourcesSolve →