Credit Card Account Operations | Dataford Interview Questions

Imagine that you're writing software for a credit card provider. Implement a program that will add new credit card accounts (Add), process charges (Charge) and credits (Credit) against them, validate card numbers (digits only, 12-16 chars; bonus: Luhn 10), and return card holder names in lexicographical order with their balance, or "error" if the card number is invalid.

Asked in the phone screen stage. Charges over limit are declined; credits may go negative; invalid cards are ignored. Reported follow-ups: validate card numbers with the Luhn algorithm.

Function

def process_transactions(transactions):

Input

transactions is a list of strings, each in one of these forms:

Add <name> <card_number> <limit>
Charge <name> <amount>
Credit <name> <amount>

Output

Return a list of strings in lexicographical order by card holder name. Each string must be "<name>: <balance>", or "error" if any card number is invalid.

Constraints

1 <= transactions.length <= 10^4
Each transaction is one of: Add, Charge, Credit
Card numbers contain only digits when valid, and have length 12 to 16 inclusive
Amounts and limits are positive integers
Card holder names are unique identifiers in the input

Function Signature

def process_transactions(transactions):

Your question is Credit Card Account Operations. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem