Banking System with Top Activity

Implement a banking system that processes a sequence of operations. Initially, the system contains no accounts. Each account has a balance and a financial-activity total, both starting at zero.

Each row of operations has one of these forms:

• ["CREATE_ACCOUNT", accountId]: If the account already exists, return false. Otherwise, create it and return true.
• ["DEPOSIT", accountId, amount]: If the account does not exist, return -1. Otherwise, add amount to its balance and activity, then return its updated balance.
• ["TRANSFER", fromAccountId, toAccountId, amount]: Return -1 if either account does not exist, both identifiers name the same account, or the sender has insufficient funds. Otherwise, move amount from the sender to the recipient, add amount to both accounts' activity, and return the sender's updated balance.
• ["TOP_ACTIVITY", n]: Return up to n account descriptions formatted as accountId(activity). Order them by activity from highest to lowest, breaking ties by accountId in ascending alphabetical order. If fewer than n accounts exist, return all accounts in that order.

An account's financial activity is the absolute sum of amounts from its successful deposits and transfers. A successful transfer contributes its amount to the activity of both endpoints. Unsuccessful transactions do not contribute activity.

Return one string array for every operation, in the same order. A scalar result is represented as a one-element array, such as ["true"] or ["2700"]; a TOP_ACTIVITY result contains its ranked account descriptions directly.

What the interview report shared

The report gave all four operation rules, the activity-ranking rule, and a complete operation/output sequence. This practice version is an estimated 95% match to that core task; the report did not include numeric limits or the original method and parameter names, so those details are not presented as source-provided.