K Closest Points to Origin

The problem. Given an array of points, where points[i] = [x, y], and an integer k, return the k points closest to the origin (0, 0), using ordinary straight-line distance √(x² + y²). The answer may be in any order, and it is unique.

Example

points = [[1,3], [-2,2]],                     k = 1  ->  [[-2,2]]
points = [[3,3], [5,-1], [-2,4]],              k = 2  ->  [[3,3], [-2,4]]
points = [[3,3], [5,-1], [-3,4], [1,1], [-3,-2]],  k = 3  ->  [[1,1], [-3,-2], [3,3]]  (any order)

Compare squared distances, x² + y². The square root never changes which point is closer, and skipping it keeps everything in exact integers — no floating-point rounding.