#hash maps

LFU cache
CodingxAI
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LRU cache where each item counts by its quantity
CodingxAI
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Per-key fixed-window cost limiter
CodingxAI
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Is a vehicle ready to go after its maintenance events?
CodingWaymo
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Link object tracks across two perception systems
CodingWaymo
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Per-position feedback for a guess against a secret word
CodingTesla
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Count subarrays with at least k equal pairs
CodingUber
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Insert, delete and get random in O(1)
CodingUberMetaxAI
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Last-click attribution
CodingUber
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Parse logs and count error codes
CodingNuro
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Construct binary tree from inorder and postorder traversal
CodingNvidia
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Streaming top-K frequent elements with O(1) updates
CodingNvidia
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Count words in a text stream
CodingNetflix
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Count pairs of words with no letters in common
CodingNetflix
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Key-value cache with per-entry TTL
CodingNetflix
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Find every set in a hand of Set cards
CodingSnowflake
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Unique and most frequent keys in a recent time window
CodingSnowflake
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Insert, delete and get random in O(1) with duplicates
CodingSnowflake
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Build reporting trees from employee-manager pairs
CodingSnowflake
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Insert delete getrandom O(1)
CodingMeta
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Palindrome permutation
CodingMeta
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Recommend accounts your followees follow
CodingMeta
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Contains duplicate within distance K
CodingMeta
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Longest substring without repeating characters
CodingMetaMicrosoftSnowflakeNetflix
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Group shifted strings
CodingMeta
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Minimum window substring
CodingMetaGoogleCharacter.AI
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Counter class with add, count and remove
CodingMeta
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Validate checkout and return logs
CodingMeta
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Contiguous array with equal 0s and 1s
CodingMeta
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Copy list with random pointer
CodingMetaMicrosoftSnowflake
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Thread-safe job registry with expiry
CodingMeta
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Top three categories by total score
CodingMeta
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Sparse matrix multiplication
CodingMetaNetflix
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Dot product of two sparse vectors
CodingMeta
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Thread-safe tally counter with bounded memory
CodingMeta
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Subarray sum equals k
CodingMeta
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Binary tree vertical order traversal
CodingMeta
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Two sum
CodingMeta
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Count user sessions from an activity log
CodingGoogle
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Settle group trip expenses with the fewest transfers
CodingGoogle
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Top K most active users from chat logs
CodingGoogle
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Two sum with the lexicographically smallest index pair
CodingGoogle
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Set with constant-time insert, delete and get random
CodingGoogle
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Recover the original array from its doubled shuffle
CodingGoogle
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Logger that reports its top K messages
CodingGoogle
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Top-k and bottom-k words in a list and in a stream
CodingGoogle
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Top K frequent elements and K closest points
CodingGoogle
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Next-word predictor from bigram counts
CodingGoogle
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Manager and peer relationships with is_manager queries
CodingGoogle
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Restaurant waitlist manager
CodingGoogle
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Is every 3+ letter piece of a string a dictionary word?
CodingGoogle
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Maximum sum of a subarray whose ends differ by k
CodingGoogle
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Process login logs split across shards
CodingGoogle
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Merge two named trees
CodingGoogle
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Predict the most frequent next word in constant time
CodingGoogle
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Duplicate detection: sliding windows, then read-heavy queries
CodingGoogle
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Most active user by distinct contacts, then top K
CodingGoogle
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Largest rectangle from a point set, any orientation
CodingGoogle
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Find timed-out RPC calls from start and end logs
CodingGoogle
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Worker hours register
CodingAmazon
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Message latency from send and receive logs
CodingAmazon
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Build a binary tree from parent-child descriptions
CodingAmazon
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Group anagrams
CodingAmazonNvidiaUber
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Unique pairs with a target sum
CodingAmazon
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Searchable sentence index
CodingAmazon
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Most common website visit pattern
CodingAmazon
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Count customers who visited on more than one date
CodingAmazon
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Earliest pair with a target sum
CodingAmazon
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Top K frequent elements
CodingAmazonAppleGoogleMeta
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Maximum frequency stack
CodingAmazon
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