Datadog Coding Interview Questions

Showing 15 problems of 100

• #67hardsometimes asked

  67. Word Ladder

  Find the shortest transformation sequence from beginWord to endWord, changing one letter at a time, using only words from a dictionary. Datadog uses this as a BFS-on-implicit-graph question — same pattern they use for shortest-path queries on dynamic service topologies.

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• #87hardfrequently asked

  87. Serialize and Deserialize Binary Tree

  Design serialize and deserialize for an arbitrary binary tree. Datadog uses this as the canonical wire-format question — same shape as their distributed metric-tree snapshot format that flows between ingest and query nodes.

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• #88hardfrequently asked

  88. Find Median from Data Stream

  Design addNum and findMedian over a streaming sequence. Datadog asks this as the canonical streaming-percentile problem — two-heap solution is the exact pattern they use for p50 over a sliding metric window.

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• #89hardfrequently asked

  89. Sliding Window Maximum

  Return the max of each sliding window of size k. Datadog asks this constantly — the monotonic deque is the exact algorithm they use for streaming max-over-window aggregations on real-time metric dashboards.

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• #90hardsometimes asked

  90. Median of Two Sorted Arrays

  Find the median of two sorted arrays in O(log(min(m,n))). Datadog asks this for the partition-based binary search — same shape as quantile estimation over two pre-aggregated metric blocks.

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• #91hardsometimes asked

  91. Regular Expression Matching

  Implement regex matching with '.' and '*'. Datadog asks this as a hard DP — same shape as their tag-pattern engine that matches user-specified wildcards against high-cardinality metric names.

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• #92hardfrequently asked

  92. Merge k Sorted Lists

  Merge k sorted linked lists into one sorted list. Datadog asks this because their query layer routinely merges K ordered metric shards into a unified stream — the min-heap pattern is identical.

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• #93hardsometimes asked

  93. Reverse Nodes in k-Group

  Reverse linked list nodes in groups of K, leaving the tail intact if it's shorter than K. Datadog uses this to test deep pointer manipulation — same shape as in-place chunk reversal in their reverse-time-order query optimization.

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• #94hardrarely asked

  94. Substring with Concatenation of All Words

  Find all starting indices of substrings that are a concatenation of each word exactly once. Datadog asks this for the hash-based sliding window — same shape as multi-tag-pattern detection on a log stream.

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• #95hardrarely asked

  95. Longest Valid Parentheses

  Find the length of the longest valid (well-formed) parentheses substring. Datadog uses this for the stack-tracking-indices trick — same shape as their balanced-segment detector on partially-corrupted log streams.

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• #96hardrarely asked

  96. Sudoku Solver

  Solve a 9x9 Sudoku via backtracking. Datadog uses this as a deep constraint-satisfaction question — same shape as their resource-allocation solver that fills a constrained schedule.

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• #97hardsometimes asked

  97. First Missing Positive

  Find the smallest missing positive integer in O(n) time and O(1) space. Datadog uses this for the index-as-hash trick — same shape as their dense-key occupancy check across a metric-ID space.

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• #98hardfrequently asked

  98. Trapping Rain Water

  Compute how much water gets trapped between bars. Datadog uses this for the two-pointer greedy proof — same shape as bounded peak-valley estimation in a streaming metric series.

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• #99hardrarely asked

  99. N-Queens

  Place N queens on an N x N board such that none attack each other. Datadog uses this as the canonical backtracking + constraint encoding question — same shape as multi-dim CSP they use for capacity placement.

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• #100hardfrequently asked

  100. Largest Rectangle in Histogram

  Find the largest rectangle area in a histogram. Datadog uses this for the monotonic-stack pattern — same shape as their algorithm for detecting the largest sustained burst window in a metric stream.

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