Prioritized Refund Allocation

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A guest is owed a refund that must be repaid from the payments they made. Each payment is [payment_id, method, time, paid], where paid is the amount in cents and method is one of "CREDIT", "CREDIT_CARD" or "PAYPAL". Earlier refunds are given as [payment_id, amount] pairs; a payment can appear in several of them, and its remaining balance is paid minus its prior refunds, never below 0.

Example 1
Input: {"refund":4500,"payments":[["p1","PAYPAL",10,5000],["p2","CREDIT_CARD",20,3000],["p3","CREDIT",5,1000],["p4","CREDIT_CARD",30,2000]],"prior_refunds":[]}
Output: [["p3","CREDIT",1000],["p4","CREDIT_CARD",2000],["p2","CREDIT_CARD",1500]]
Explanation: CREDIT comes first, so p3 gives its full 1000. Next is CREDIT_CARD, newest first: p4 (time 30) gives 2000. That leaves 1500, and p2 (time 20) gives 1500 of its 3000. PAYPAL is not touched.

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Prioritized Refund Allocation

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Example 1

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