How should I practice Restaurant Waitlist?

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

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Restaurant Waitlist

Google● HardNEW GRADPHONE SCREENONSITE INTERVIEW

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Problem statement

Process operations against an initially empty restaurant waitlist.

JOIN id size adds a party with a unique string ID and positive party size to the back of the waitlist.
DELETE id removes the named party, which is guaranteed to be waiting.
SERVE tableSize removes and returns the earliest still-waiting party whose size is at most tableSize. Return NONE when no party fits.

Only SERVE operations produce output. Return those party IDs in operation order.

Function

processWaitlist(operations: String[][]) → String[]

Examples

Example 1

operations = [["JOIN","A","4"],["JOIN","B","2"],["JOIN","C","6"],["SERVE","3"],["DELETE","A"],["SERVE","6"],["SERVE","10"]]return = ["B","C","NONE"]

Party B is the first party that fits a table of size 3. After deleting A, party C is served next.

Example 2

operations = [["JOIN","P1","5"],["JOIN","P2","2"],["JOIN","P3","2"],["SERVE","2"],["SERVE","5"]]return = ["P2","P1"]

P2 is earlier than P3 among parties that fit size 2. The next table can seat the earlier remaining party P1.

Constraints

1 <= operations.length <= 100000.
Party IDs contain letters or digits, have length from 1 through 20, and are unique across the entire operation sequence.
Party sizes and table sizes are integers from 1 through 100000.
Every DELETE operation names a currently waiting party.