Top 50 Hash Tables Interview Questions
The most frequently asked Hash Tables questions across all roles and companies, ranked by real interview frequency. Updated daily.
Use a hash map to find two array elements that sum to a target in O(n) time.
iCapital
Paycom
Blend360Find the first non-repeating character in a string using frequency counting and a second pass in O(n) time.
Cloudsek
Brightside Health
McAfeeFind the longest substring with all unique characters using a sliding window.
DeepInstinct
Taboola
EDF RenewablesUse a sliding window and hash map to find the longest substring without repeated characters in a string.
Insight Global
O'Reilly Media
AvisoUse a hash map to find two array elements that sum to a target in O(n) time.
EtsyLLuxoft Singapore
NeoDoctoFind two indices in an array whose values add up to a target using a hash map.
Converseon
Earnest ResearchEtsyUse Floyd’s two-pointer algorithm to determine whether a singly linked list contains a cycle.
Sigmoid
AMD Construction Group
InformaticaImplement an LRU cache in O(1) average time using a hash table and doubly linked list.
Allianz
ICF
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