18 lines
606 B
Python
18 lines
606 B
Python
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class Ledger:
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def __init__(self) -> None:
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self._balances: dict[str, int] = {}
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self._applied: set[str] = set()
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def balance(self, account: str) -> int:
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return self._balances.get(account, 0)
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def apply(self, operation_id: str, account: str, delta: int) -> int:
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if operation_id in self._applied:
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return self.balance(account)
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self._applied.add(operation_id)
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updated = self.balance(account) + delta
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if updated < 0:
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raise ValueError("insufficient funds")
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self._balances[account] = updated
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return updated
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