How should I practice Total Active Time by Space?

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

Is Total Active Time by Space associated with xAI?

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

Problem · Hash Table

Total Active Time by Space

Learn this problem

● Medium

xAIFULLTIMEONSITE INTERVIEW

Problem statement

Process records in nondecreasing timestamp order. Each record is [operation, space, user, timestamp].

create creates a new Space and makes its creator active at that timestamp.
join makes an inactive user active in an existing Space.
leave ends that user's current active interval in the Space.

The active-time contribution of a completed interval is leaveTimestamp - startTimestamp. Sum every user's completed intervals for each Space.

Return one string space:total per observed Space, ordered by Space name in ascending lexicographic order. Timestamps and totals use 64-bit integer arithmetic.

Function

totalSpaceActiveTime(records: String[][]) → String[]

Examples

Example 1

records = [["create","abc","user_1","1234567000"],["join","abc","user_2","1234567100"],["leave","abc","user_2","1234567300"],["create","def","user_2","1234568000"],["leave","def","user_2","1234568500"],["leave","abc","user_1","1234569000"]]return = ["abc:2200","def:500"]

In abc, user_1 contributes 2000 and user_2 contributes 200. In def, user_2 contributes 500.

Example 2

records = [["create","alpha","u1","5"],["leave","alpha","u1","5"],["join","alpha","u1","8"],["leave","alpha","u1","13"],["create","beta","u2","10"],["leave","beta","u2","12"]]return = ["alpha:5","beta:2"]

A user may rejoin after leaving. The zero-duration first interval in alpha contributes nothing; its second interval contributes 5.

Constraints

1 <= records.length <= 200000.
Every record has exactly four strings.
operation is create, join, or leave.
0 <= timestamp <= 10^18, and timestamps are nondecreasing.
Space and user names are non-empty ASCII strings without :.
Every create or join has exactly one later matching leave; lifecycle operations are valid.