How should I practice Friendship and Balance Tracker?

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

Is Friendship and Balance Tracker associated with Robinhood?

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

Friendship and Balance Tracker

Robinhood● MediumFULLTIMEONSITE INTERVIEW

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Problem statement

Process API-like operations in order. Each begins with a unique request id.

id REGISTER user balance creates a user.
id REQUEST from to creates a pending friend request stored under this id.
id ACCEPT requestId accepts and consumes that pending request.
id TRANSFER from to amount moves money only between accepted friends when the sender has enough balance.

Return id OK for a successful non-transfer, id OK senderBalance receiverBalance for a successful transfer, or id REJECTED. Rejected operations do not change state.

Function

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

Examples

Example 1

operations = ["1 REGISTER a 100","2 REGISTER b 0","3 REQUEST a b","4 ACCEPT 3","5 TRANSFER a b 30"]return = ["1 OK","2 OK","3 OK","4 OK","5 OK 70 30"]

The accepted friendship authorizes the affordable transfer.

Example 2

operations = ["r1 REGISTER a 10","r2 REGISTER b 0","r3 TRANSFER a b 1"]return = ["r1 OK","r2 OK","r3 REJECTED"]

Registered users are not friends by default.

Example 3

operations = ["1 REGISTER a 5","2 REGISTER a 9"]return = ["1 OK","2 REJECTED"]

Duplicate registration is rejected without replacing the balance.

Constraints

1 <= operations.length <= 2 * 10^5.
Ids and usernames contain no spaces; request ids are unique.
Balances and amounts fit signed 64-bit integers.