Parse JSON

Compute the total amount of non-canceled external USD transactions from a stream of JSON records as fast as possible.

Input: 1 000 000 JSON records on STDIN, one per line. Each record has the following structure:

{
    "user_id": 0,
    "currency": "USD",
    "transactions": [
        {
            "amount": 0,
            "to_user_id": 0,
            "canceled": false
        }
    ]
}

Field order is not guaranteed within any object.

Output: The total amount of all transactions where:

• record.currency == "USD"
• transaction.to_user_id != record.user_id (external)
• transaction.canceled is false or absent