Maintain a list of points around a center point, preserving CCW order

问题

I have the following class:

 public class Vertex() {
    private double xCoord;
    private double yCoord;
    private ArrayList<Vertex> neighborList();
 }

And I want to support adding/removing vertices to the neighborList such that the points are listed in CCW order around this vertex (which point is first in the list doesn't matter). If points are collinear, nearer points to this should be first. I've tried several methods but so far have always been able to find a counter example that doesn't work for the given method.

Does anyone have a good idea of how to do this in a simple and efficient manner?

回答1:

Express the point coordinates in the polar form

t = atan2(Y-Yo, X-Xo)
r = sqrt((X-Xo)^2 + (Y-Yo)^2)

and use lexicographical ordering on angle then radius.

来源：https://stackoverflow.com/questions/9336682/maintain-a-list-of-points-around-a-center-point-preserving-ccw-order