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Top 50 efficiency Interview Questions

The most frequently asked efficiency questions across all roles and companies, ranked by real interview frequency. Updated daily.

50questions
~16htotal time
223companies covered
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1
CodingStart here. 34 questions · ~634 min
Implement Rate Limiter AlgorithmHard
Practice
Recently asked

Implement a per-client sliding-window rate limiter using hash maps and queues.

rate limitingefficiencyDatadogTikTokDave
Find Duplicate Elements EfficientlyMedium
Practice

Find each duplicated integer once using a hash set and preserve its first duplicate order.

deduplicationArraysefficiencyHHCLTech MexicoSSynackPayU
Efficient JSON TransformationsHard
Practice

Recursively filter Palo Alto Networks JSON by blocked paths using a trie to prune excluded subtrees efficiently.

efficiencyPalo Alto NetworksPersistent Systems
Group Objects by PropertyEasy
Practice
Recently asked

Group Amazon Alexa event objects by a hashable property while preserving the original order within each group.

ArraysefficiencyAmazonInformatica
Efficient Traversal of Complex StructuresMedium
Practice

Return the path to a Bloomberg Terminal topic in a nested hierarchy using iterative depth-first search.

efficiencytraversalBloombergEthos Life
Reverse Bits of a 32-Bit NumberMedium
Practice
Recently asked

Reverse all 32 bits of an unsigned integer using constant-time bitwise mask operations.

coding challengeBit ManipulationefficiencyKeysight Technologies
Efficient Coding ChallengeHard
Practice

Count valid Unity asset build orders with prerequisite constraints using bitmask dynamic programming.

efficiencyUnityUnity Technologies
Array Intersection ImplementationEasy
Practice

Find distinct identifiers shared by two arrays using a hash set while preserving the first array's order.

ArraysProgrammingefficiencyPPiping Rock Health ProductsNorth Carolina
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2
Behavioral & Leadership6 questions · ~112 min
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3
Execution4 questions · ~75 min
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4
More topics6 questions · ~112 min
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Hands-on SQL practiceWrite and run real queries in the editor. 3 drills · ~30 min
Anagram Check With SQLMedium
Practice
Practice drill

Compare normalized character signatures to determine whether each pair of strings is an anagram.

data cleaningJoinsstring manipulationAdobe
Sum From 1 to 1,000,000Easy
Practice
Practice drill

Calculate the sum of integers from 1 to 1,000,000 using PostgreSQL aggregation and filtering.

AlgorithmsVirtu Financial
SQL Duplicate Record CleanupMedium
Practice
Recently asked
Practice drill

Identify duplicate transaction rows, retain the earliest record, and delete later duplicates safely.

deduplicationdata cleaningtransactionsOracleDiscoverMicrosoft
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