SeedGenerator.cs

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;

namespace Clusterization_algorithms
{
    /// <summary>
    /// Weighed random with points to k-means++ algorithm
    /// Allows to calculate optimal start positions to seeds
    /// </summary>
    public class SeedGenerator
    {
        private Dictionary<Point, double> _points = new Dictionary<Point, double> { }; // <point, weight>; Weight is equal to distance
        public int _seedCount = 2;
        private Random _rand = new Random();
        private List<Point> _seeds = new List<Point> { };
        private double _sumOfWeight = 0;

        public SeedGenerator()
        {
        }

        public SeedGenerator(Dictionary<Point, int> points, int seedCount)
        {
            SetPoints(points);
            _seedCount = seedCount;
        }

        public List<Point> GetSeeds()
        {
            int rnum = _rand.Next(0, _points.Count - 1);
            Point seed1 = _points.ElementAt(rnum).Key; // get 1-st random seed from points
            _seeds.Add(seed1);                         // add point to seed list
            _points.Remove(seed1);                     // remove this point from points

            CalculatePointsWeight(seed1);

            for (int i = 1; i < _seedCount; i++)
            {
                FindNewSeed();
            }

            return _seeds;
        }

        private void FindNewSeed()
        {
            SortPoints();

            double rsum = _rand.Next(0, (int)_sumOfWeight);

            for (int i = 0; i < _points.Count; i++)
            {
                var pair = _points.ElementAt(i);

                if (pair.Value >= rsum)
                {
                    _seeds.Add(pair.Key);
                    _points.Remove(pair.Key);
                    CalculatePointsWeight(pair.Key);
                    break;
                }

                rsum -= pair.Value;
            }
        }

        private void SortPoints()
        {
            Dictionary<Point, double> newPoints = new Dictionary<Point, double> { };

            foreach (var pair in _points.OrderBy(ppair => ppair.Value))
            {
                newPoints.Add(pair.Key, pair.Value);
            }
            _points = newPoints;
        }

        private void CalculatePointsWeight(Point seed)
        {
            Dictionary<Point, double> newPoints = new Dictionary<Point, double> { };
            _sumOfWeight = 0;

            for (int i = 0; i < _points.Count; i++)
            {
                Point point = _points.ElementAt(i).Key;
                double weigh = _points.ElementAt(i).Value;

                double dist = Calculator.CalcDistance(seed, point);
                weigh += dist;
                _sumOfWeight += weigh;

                newPoints.Add(point, weigh);
            }
            _points = newPoints;
        }

        public void SetPoints(Dictionary<Point, int> dictionary)
        {
            _points.Clear();

            foreach (var pair in dictionary)
            {
                _points.Add(pair.Key, 0);
            }
        }

        public String PrintPoints()
        {
            String str = "";

            Console.WriteLine("Points list:");

            foreach (var point in _points)
            {
                Console.WriteLine(point.ToString());
                str += point.ToString() + "\n";
            }

            Console.WriteLine();
            return str;
        }

        public void PrintSeeds()
        {
            Console.WriteLine("Print seeds:");

            foreach (Point seed in _seeds)
            {
                Console.WriteLine(seed.ToString());
            }

            Console.WriteLine();
        }
    }
}