Transaction Fraud Report Part 2 — High-Risk Rule Validation

Four-part sequence: This is Part 2 of one progressive transaction-fraud interview exercise. It retains Part 1 and adds two high-risk rules.

1. Part 1: Verify Transaction Data Integrity.
2. Part 2: High-Risk Rule Validation (you are here).
3. Part 3: User Behavior Matching.
4. Part 4: Smart Fraud Error Reporting.

Validate transaction integrity, then apply amount and payment-method risk rules.

Input

Each string in transactions is one unquoted CSV row with exactly six comma-separated fields, in this order: transaction_id,user_id,amount,payment_method,country,hour. Trim surrounding whitespace from every field.

For a row whose fields are all non-empty, amount is a valid decimal integer. The inclusive interval [normalMin, normalMax] defines the normal amount range. Membership in blockedMethods is case-sensitive.

Review rules

1. If any field is empty after trimming, mark the row SUSPICIOUS and do not parse or apply later rules.
2. Otherwise, mark the row SUSPICIOUS when its amount is outside [normalMin, normalMax] or its payment method occurs in blockedMethods.
3. Mark every remaining row OK.

Result

Return a two-column string table whose first row is ["transaction_id","status"]. Append one result row per transaction in input order, preserving repeated IDs and an empty ID on an invalid row.