I don't know relevant keywords about this algorithm. I can show you visually Sort elements like circular pattern

Second image is result

Any ideas are appreciated

  • 3
    $\begingroup$ ("scan|sweep line" or "line|plane scan|scanning|sweep|sweeping" and "polar coordinates"?) Are you looking for terminology or algorithm? Tag accordingly! $\endgroup$
    – greybeard
    Feb 25, 2020 at 9:11
  • 1
    $\begingroup$ Take a look at stackoverflow.com/questions/6989100/… $\endgroup$
    – ciamej
    Feb 25, 2020 at 17:12
  • 1
    $\begingroup$ This reminds me of parts of the Jarvis March algorithm or Graham scan for convex hull calculation. Maybe these articles will give you some additional wording clues. $\endgroup$ Feb 25, 2020 at 22:38

2 Answers 2


For each of your points in the field, calculate the red angle: enter image description here

Then sort all the (point, angle)-tuples by the angle.


Here's a way to sort points by angle in Swift:

let radarSortedPoints: [CGPoint] = points.sorted { pointA, pointB -> Bool in
    atan2(pointA.y, pointA.x) < atan2(pointB.y, pointB.x)
  • 4
    $\begingroup$ Just a note, the use of atan2 is not necessary, see github.com/Laakeri/contestlib/blob/master/src/geometry/… for an implementation that is exact for integers. $\endgroup$
    – Laakeri
    Feb 25, 2020 at 9:55
  • $\begingroup$ @Laakeri Isyourspacekeybroken? lol why would you type def something as clear as complex<long long> to something as arbitrary and cryptic as co? $\endgroup$
    – Alexander
    Feb 25, 2020 at 23:37

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