You are implementing an in-memory credit ledger for a shared GPU pool. Each event changes one tenant's credit balance. Use the event schema: (eventId, tenantId, delta) - eventId: unique identifier for idempotency - tenantId: tenant whose balance changes - delta: signed integer; positive adds credits, negative deducts credits Business rules: 1. A tenant's balance may never go below 0. If applying an event would make the balance negative, reject that event. 2. Idempotency is required. If the same eventId is seen again, it must not change state a second time. Instead, return the same success/failure result that was produced the first time that eventId was processed. 3. During initialization, apply the initial events in order using the same rules. 4. getBalance for an unknown tenant should return 0. For the online judge, implement a single function: solution(init_events, operations) - init_events is the ordered list passed to init(events) - operations is a list of later actions, each of which is either: - ('get', tenantId) - ('apply', (eventId, tenantId, delta)) Return a list of outputs for the operations, in order: - For ('get', tenantId), append the current integer balance. - For ('apply', event), append True if that event is accepted, or False if it is rejected. If it is a duplicate eventId, append the same boolean result as the first time it was processed. Follow-up discussion (not required in code): be ready to explain your O(1)-average data structures, how you would make updates thread-safe, and how you would persist the ledger for crash recovery using techniques such as a write-ahead log plus snapshots.

def solution(init_events, operations):
    balances = {}
    event_result = {}

    def process_event(event):
        event_id, tenant_id, delta = event

        if event_id in event_result:
            return event_result[event_id]

        new_balance = balances.get(tenant_id, 0) + delta
        accepted = new_balance >= 0

        if accepted:
            balances[tenant_id] = new_balance

        event_result[event_id] = accepted
        return accepted

    for event in init_events:
        process_event(event)

    result = []
    for op in operations:
        if op[0] == 'get':
            tenant_id = op[1]
            result.append(balances.get(tenant_id, 0))
        elif op[0] == 'apply':
            event = op[1]
            result.append(process_event(event))
        else:
            raise ValueError('Unknown operation type')

    return result