Choose Extreme Shipment Weights

Context

A freight hub is preparing a special loading list. From the recorded weights of incoming shipments, it must keep the lightest k shipments and the heaviest k shipments. The list is organized by weight, duplicate weights remain separate, and a shipment position that belongs to both groups is included only once.

Problem

Given an integer array shipments and an integer k, return the shipment weights occupying the first k and last k positions after sorting shipments in nondecreasing order. Preserve every selected occurrence, including duplicate values. If the two selected ranges overlap, include each array position only once. When k is zero or shipments is empty, return an empty array. The returned array must remain in nondecreasing order.

Examples

Constraints

• 0 <= len(shipments) <= 100000
• -1000000000 <= shipments[i] <= 1000000000 for every i
• 0 <= k <= len(shipments)
• Types: shipments is int[], k is int; result is int[]

Function signature

def select_extreme_shipments(shipments: list[int], k: int) -> list[int]

shipments list[int]

Weights of shipments recorded at the hub.

k int

Number of positions to select from each end of the sorted shipment list.

returns list[int]

The sorted shipment weights from the first k and last k sorted positions, with overlapping positions included once and duplicate occurrences preserved.

Notes

• Selection is based on sorted positions, not distinct weight values.
• If the low-end and high-end ranges overlap, their union is returned without duplicating an overlapping position.