Deduplication

Task

Implement deduplication(values: list[int]) -> list[int]. Remove duplicate integer identifiers while preserving the order of their first occurrences.

Requirements

• Return each distinct value exactly once.
• Keep the first occurrence of each value and discard all of its later occurrences.
• Preserve first-occurrence order; do not sort the result.
• Treat negative, zero, and positive integers as ordinary identifiers.
• Return an empty output for empty input.
• Do not mutate the input.

Example

deduplication([4, 2, 4, 1, 2, 3])
# [4, 2, 1, 3]