Meta Software Engineer Interview Questions (2026)

Recurse with min/max bounds rather than just comparing parent-child. State why the naive parent-child check fails. Meta rewards getting the correct invariant fast and stating the edge cases (duplicates, single node).

Min-heap of k heads (O(N log k)) or divide-and-conquer pairwise merge. Code it cleanly and quickly — this is a common first problem and interviewers watch how fast you reach working code.

Prefix-sum + hash map of counts in O(n). Explain why the running-sum-difference trick works. A frequent Meta problem that separates candidates who pattern-match prefix sums from those who brute force.

Level-order BFS taking the last node per level, or DFS tracking depth. Both O(n). Narrate while coding — Meta explicitly values talking through the solution as you type.

Prefix sums + binary search on a random draw. Walk the probability reasoning. A Meta favorite because it tests whether you can map a probability requirement onto a clean data structure.

Clarify scale and ranking scope. Discuss fan-out-on-write vs fan-out-on-read, the celebrity problem, caching, and ranking as a separable service. Meta's design round wants product-aware architecture, not just plumbing.

Walk both lists with a carry, build the result node by node. O(max(m,n)). Handle the trailing carry edge case — interviewers check it deliberately.

STAR. Meta's behavioral round screens for handling conflict directly and constructively, plus the impact of the resolution. Choose a story where you disagreed, engaged respectfully, and drove a concrete outcome.