How should I practice Who Is in the Room??

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

Is Who Is in the Room? associated with WhatNot?

FastPrep tags this as a WhatNot phone screen coding practice problem when the problem catalog has that company and stage context.

Who Is in the Room?

WhatNot● MediumINTERNPHONE SCREEN

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Problem statement

Given an ordered event log, determine which observed people are inside a room after all events.

For this exercise, each event is [name, action], where action is enter or exit. Everyone starts outside. An entry sets that person's state to IN; an exit sets it to OUT. Repeating the same action is allowed and does not change its meaning.

Return one row [name, state] for every person appearing in the log, including people who finish outside. Sort rows lexicographically by name. The answer for an empty log is an empty array.

Function

roomPresence(events: String[][]) → String[][]

Examples

Example 1

events = [["amy","enter"],["bob","enter"],["amy","exit"]]return = [["amy","OUT"],["bob","IN"]]

Amy's latest event is an exit; Bob's is an entry. Rows are ordered by name.

Example 2

events = [["zoe","exit"],["zoe","enter"],["zoe","enter"]]return = [["zoe","IN"]]

An entry sets the state to IN. Repeated entries keep the same state.

Example 3

events = []return = []

No observed people means no output rows.

Constraints

For this exercise, assume 0 <= events.length <= 200.
Every event has exactly two strings.
Names contain 1 to 20 lowercase English letters.
Actions are exactly enter or exit.