
Design and implement a banking ledger for n accounts labeled 1..n with initial balances. Provide an API: deposit(id, amount) -> bool, withdraw(id, amount) -> bool, transfer(fromId, toId, amount) -> bool. Rules: return false for invalid account IDs or insufficient funds; otherwise apply updates and return true. Constraints: up to 200,000 operations, amounts up to 10^12, target O(