Trace [[3,3], [5,-1], [-2,4]] with k = 2.
Squared distances: [3,3] → 18, [5,-1] → 26, [-2,4] → 20.
Process [3,3] (dist 18): heap = [(18, [3,3])].
Process [5,-1] (dist 26): heap = [(26, [5,-1]), (18, [3,3])]. Max-heap, so 26 is at top.
Process [-2,4] (dist 20): 20 < 26 (heap max). Remove [5,-1], add [-2,4].
Heap = [(20, [-2,4]), (18, [3,3])].
Return [[3,3], [-2,4]] (any order).
time: process points, each heap operation is . space for heap.