Two-account transfer matching

Python data engineering interview problem. Difficulty: intermediate. Pattern: Hashing. About 15 minutes. Part of the Pro drill bank.

Two ledger lines should pair when their amounts add to a target transfer size. Accounting wants those two indices (or values) if they exist.

Find two amounts that add to the target transfer (two-sum on the list).

Requirements

• Use each position at most once unless tests allow it.
• Return the pair or indices the tests specify.

Constraints

• amounts: list of numbers.
• No pair: return the documented sentinel.
• Duplicates of the same amount may or may not pair with themselves.

Examples

Input: complementary_pair([1, -1, 2]) Output: [0, 1] This input follows the stated rules and produces this output.

Topics: lakebench, python, hash-based-problems.

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