Splitwise
Design an expense-sharing app with pluggable split strategies, exact money arithmetic and a debt-simplification step.
Requirements
Clarify, then fix the scope:
- Users share expenses in a group. One person pays; the cost is split among some members.
- Three split types: equal, exact (stated amounts) and percent.
- The app can show each person's balance: how much they are owed or owe.
- Simplify debts: reduce the number of payments needed to settle everyone.
- Amounts must never drift by a fraction of a paisa.
Out of scope: login, several currencies, multiple payers, notifications, storage.
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