How should I practice LFU Cache?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Blinkit onsite interview problems in FastPrep.

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FastPrep tags this as a Blinkit onsite interview coding practice problem when the problem catalog has that company and stage context.

Problem · Design

LFU Cache

Learn this problem

● Hard

BlinkitFULLTIMEONSITE INTERVIEW

Problem statement

Process commands on an initially empty least-frequently-used cache with positive integer capacity.

put key value inserts a new key or updates an existing key.
get key returns the stored value, or -1 when the key is absent.

For this exercise, assume a successful get and a put that updates an existing key each increase that key's frequency by one and make it most recently used within its new frequency. A new key starts with frequency one.

When a new insertion would exceed capacity, evict the key with the smallest frequency. Break a frequency tie by evicting the least recently used key. Return the results of all get commands in order. Each operation should run in average O(1) time.

Function

processLfuCache(capacity: int, operations: String[]) → int[]

Examples

Example 1

capacity = 2operations = ["put 1 1","put 2 2","get 1","put 3 3","get 2","get 3","put 4 4","get 1","get 3","get 4"]return = [1,-1,3,-1,3,4]

Reading key 1 raises its frequency, so key 2 is evicted first. Later keys 1 and 3 tie on frequency, and key 1 is least recent.

Example 2

capacity = 1operations = ["put 7 5","put 7 8","get 7","put 9 4","get 7","get 9"]return = [8,-1,4]

Updating key 7 changes its value and frequency. Inserting key 9 into a one-entry cache then evicts key 7.

Constraints

1 <= capacity <= 3000.
1 <= operations.length <= 2 * 10^4.
Each command is exactly get key or put key value.
Keys and values fit in signed 32-bit integers.
At least one command is get.