Combine Vectors(MLE)
Reported by candidates from Meta's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
Meta's Combine Vectors problem showed up in February 2024 assessments, and it's a deceptively simple prompt that catches candidates off guard. You're given vectors (likely arrays or lists of numbers) and need to combine them into a single output. The trick isn't complex logic, it's figuring out what "combine" means in Meta's context. They often want you to merge, concatenate, or produce some aggregate without spelling it out. StealthCoder will read the exact spec on screen and surface the pattern in seconds if you blank on the wording.
Pattern and pitfall
Vector problems at Meta usually fall into one of three buckets: concatenation (merge arrays in order), aggregation (sum or multiply across dimensions), or interleaving (zip elements together). Without the full problem text, the safest assumption is concatenation with a twist, maybe you're combining vectors while maintaining order, or deduplicating, or handling edge cases like empty inputs. The pattern is typically array or simulation-based. The edge case that trips people up is how to handle mismatched vector lengths or null/empty vectors. When you're live on the OA, StealthCoder acts as a safety net: if the problem statement is ambiguous, it'll flag the likely intent and show you the skeleton fast so you can code with confidence.
If you see this problem in your OA tomorrow, the play is to recognize the pattern in 30 seconds. StealthCoder buys you that recognition.
You can drill Combine Vectors(MLE) cold, or you can hedge it. StealthCoder runs invisibly during screen share and surfaces a working solution in under 2 seconds. The proctor sees the IDE. They don't see what's behind it. Built by an Amazon engineer who passed his OA cold and still thinks the filter is broken.
Get StealthCoderRelated leaked OAs
This OA pattern shows up on LeetCode as merge sorted array. If you have time before the OA, drill that.
You've seen the question.
Make sure you actually pass Meta's OA.
Meta reuses patterns across OAs. Built by an Amazon engineer who passed his OA cold and still thinks the filter is broken. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Combine Vectors(MLE) FAQ
Is this a math problem or a data structure problem?+
It's data structure. You're manipulating arrays or lists, not doing linear algebra. The word 'vector' here just means a 1D array. Focus on how to merge or combine sequences, not on dot products or matrix operations.
What's the most common gotcha in Meta's vector problems?+
Edge cases. Empty vectors, single-element vectors, or very large inputs. Also, the problem statement is often vague about the output format. Read the examples carefully. If there are none, that's a red flag, ask for clarification or infer from the function signature.
How do I prepare for this in 24 hours?+
Review array concatenation, merging, and interleaving. Practice on two-pointer merges and basic list flattening. Don't overthink it. Most combine problems are O(n) or O(n log n). If you're stuck during the OA, pseudocode the merge step first, then code.
Do I need to optimize space, or is time the priority?+
Meta usually cares about both, but time comes first. An O(n) solution with O(n) space is standard. If the problem asks for in-place, they'll say so explicitly. Don't spend 30 minutes chasing O(1) space unless the prompt demands it.
Is this problem still commonly asked at Meta in 2024?+
Yes. Vector and array manipulation problems are evergreen at Meta, especially in ML or backend roles. The exact title may vary, but the core pattern, merge, combine, or aggregate sequences, stays consistent across cycles.