Level 1: Basic Account Operations

Implement three functions: CreateAccount, Deposit, and Withdraw.

CreateAccount

def CreateAccount(timestamp, accountId):
    # Create a new account with the given accountId and initialize balance to 0

Deposit

def Deposit(timestamp, accountId, amount):
    # Deposit the given amount into the account
    # Edge Case: If the account does not exist, handle appropriately

Withdraw

def Withdraw(timestamp, accountId, amount):
    # Withdraw the given amount from the account
    # Edge Case: If the account does not exist or balance is insufficient, handle appropriately

Level 2: TopActivity

Implement a function to return the top N accounts based on the number of operations (both deposit and withdraw).

TopActivity

def TopActivity(n):
    # Return a list of top n accounts sorted by the number of operations
    # Each operation counts equally, whether it is deposit or withdraw

Note: Initially it might seem like the sorting is by balance, but it is actually by operation count.

Level 3: Transfer with Acceptance

Implement transfer-related functionality with a 24-hour acceptance window.

Transfer

def Transfer(timestamp, sourceAccountId, targetAccountId, amount):
    # Initiate a transfer of amount from source to target
    # Balance of source is immediately reduced upon calling Transfer
    # Transfer must be accepted within 24 hours by the target

AcceptTransfer

def AcceptTransfer(timestamp, targetAccountId, amount):
    # Target account explicitly accepts the transfer within 24 hours
    # If not accepted, the transfer becomes invalid

Explanation

• When Transfer is called, the source account’s balance is immediately deducted, even before AcceptTransfer.
• If AcceptTransfer is not called within 24 hours, the transfer is canceled or invalidated, but the balance handling logic might need compensation later.
• Based on the unit tests, the expectation is that balance deduction happens immediately on transfer initiation, not after acceptance.

Level 4: Merge Accounts

Merge two accounts into one.

Although details were not provided, typically a MergeAccount function would look like:

MergeAccount

def MergeAccount(timestamp, sourceAccountId, targetAccountId):
    # Merge source account into target account
    # Transfer balance and possibly transaction history
    # Source account is closed after merging

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