Fastest way to sort an Array c#

Question

Hi this is my problem I have an array of points P(x,y) and I need to sort these points from the furthest to the closest, respect to the barycenter of a Polygon, this what I have done (I know this is a bad solution ) how can I do a better and aboveall faster solution?

List<C2DPoint> OrderedGripperPoints = new List<C2DPoint> { };

while(myGripperPoints.Count!=0) 
{
    double dist=-1;
    int index=-1;
    for(int k=0;k<myGripperPoints.Count;k++)
    {
        if(myGripperPoints[k].Distance(WorkScrap.GetCentroid())>=dist)
        {
            index = k;
            dist = myGripperPoints[k].Distance(WorkScrap.GetCentroid());
        }
    }

    OrderedGripperPoints.Add(myGripperPoints[index]);
    myGripperPoints.RemoveAt(index);
}

Thanks for your answers...

Is it possible to precompute distance at creation time of C2DPoint? — Niyoko
– Niyoko, Commented Oct 27, 2016 at 6:58

selami · Accepted Answer · 2016-10-27 07:00:00Z

4

Use Linq to order points.

using System.Linq;

var sortedList = myGripperPoints.OrderBy(p => p.Distance(WorkScrap.GetCentroid())).ToList();

answered Oct 27, 2016 at 7:00

selami

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2 Comments

Alessio Il Pierce Giannelli Over a year ago

Thanks for the answer

Mrinal Kamboj Over a year ago

It should be OrderByDescending, based on the question posted

Mrinal Kamboj · Accepted Answer · 2016-10-27 11:03:14Z

1

Consider the following code:

Point Class (assumed class definition)

class Point
{
    public int X { get; set;}

    public int Y { get; set;}   
}

Point EqualityComparer

class PointEqualityComparer : IEqualityComparer<Point>
{
    public bool Equals(Point p1, Point p2) { return p1.X == p2.X && p1.Y == p2.Y; }

    public int GetHashCode(Point p) { return p.X.GetHashCode() *31 + p.Y.GetHashCode()*23; }
}

Create a Dictionary with Point as Key and Distance as value (assuming integer):

Dictionary<Point,int> pointDictionary = 
new Dictionary<Point, int>(new PointEqualityComparer());

Add Points as follows:

Point p = new Point {X = <value>, Y = <value>};
pointDictionary.Add(p,p.Distance(WorkScrap.GetCentroid()));

Order by Distance as follows:

pointDictionary.OrderByDescending(x => x.Value).ToList();

Ordering is done by Distance in Descending order as expected
Result would be List<KeyValuePair<Point,int>>, where elements are in Descending order

edited Oct 27, 2016 at 11:03

answered Oct 27, 2016 at 7:20

Mrinal Kamboj

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2 Comments

Mrinal Kamboj Over a year ago

This solution provides you much more fine grain control over the process of Ordering as many more properties can be part of the Dictionary <key,value> and can be used in the Ordered collection

Mrinal Kamboj Over a year ago

@AntonínLejsek thanks for pointing out, is this one better. Guarantee of having unique hash still may not be there, but will reduce the clash

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