How should I practice Directly Linked Users?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Stripe online assessment problems in FastPrep.

Is Directly Linked Users associated with Stripe?

FastPrep tags this as a Stripe online assessment coding practice problem when the problem catalog has that company and stage context.

Problem · Hash Table

Directly Linked Users

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Problem statement

Financial crimes are rarely committed in isolation. Bad actors may spread activity across multiple user accounts, but shared identifiers can reveal connections.

Each transaction log entry is formatted as user_id,device_id. Two different users are directly linked if they use the same device. A single user may appear multiple times with different devices.

Given the log and a target user, return all users directly linked to the target user. The target user should not appear in the output. Return the user IDs in lexicographic order.

Function

findDirectlyLinkedUsers(transactions: String[], targetUser: String) → String[]

Complete findDirectlyLinkedUsers.

String transactions[n]: transaction rows formatted user_id,device_id
String targetUser: the user to investigate

Returns

String[]: directly linked users.

Examples

Example 1

transactions = ["Alice,D1","Bob,D1","Charlie,D2","David,D3","Eve,D1"]targetUser = "Alice"return = ["Bob","Eve"]

Alice used D1. Bob and Eve also used D1.

Example 2

transactions = ["Alice,D1","Alice,D2","Bob,D2","Cara,D3"]targetUser = "Alice"return = ["Bob"]

Alice is associated with D1 and D2, and Bob shares D2.

Constraints

0 <= transactions.length <= 10^5
User IDs and device IDs contain no commas.