Validate Expense Reimbursements (Legality Check)

Problem: Validate Expense Reimbursements (Legality Check) You are given a list of employee expense reimbursement records. Implement validation logic to determine whether each reimbursement is legal/valid, and output the validation result for each record. Input The input contains multiple reimbursement records. Each record contains at least the following fields: employee_id: employee identifier (string or integer) amount: reimbursement amount (integer or float) category: expense category (string) timestamp: submission time (ISO8601 string or integer timestamp) receipt_id: receipt/invoice identifier (string) Note: The interview write-up does not specify the exact format; it could be a JSON array, CSV, or line-based text. Output For each reimbursement record (in the same order as input), output whether it is valid: Return a list of results. Each result should contain at least: is_valid: boolean (optional) reason: string describing why it is invalid Validation rules (to be provided in the interview) Implement the rules given by the interviewer. Common examples (possible directions only): Amount must be positive. Category must be in an allowed set. Duplicate receipt_id is not allowed. Timestamp must be within an allowable window (e.g., last 90 days). Per-transaction / per-day / per-month limits. Constraints Not provided in the write-up; typical expectations: number of records n up to 1e4–1e5 aim for O(n) or O(n log n) Example test ideas (illustrative only) Negative amount -> invalid. Two records share the same receipt_id -> at least one invalid. Category not allowed -> invalid. Timestamp out of window -> invalid. Mixed valid/invalid records -> output per-record results. Example Input [{'employee_id': 'e1', 'amount': -10, 'category': 'MEAL', 'timestamp': '2026-01-01T10:00:00Z', 'receipt_id': 'r1'}] Output [{'is_valid': false}]