C# 创建KD树的程序

实现了KD平衡树的程序，由于MATLAB实现需要用到引用类型或者采用循环实现(见MATLAB的KDTreeSearcher.m),因此采用C#来实现

using System;using System.Collections.Generic;using System.Linq;namespace KNNSearch{    /// 
    /// Description of KNN.    /// 
    public class KNN    {        /// 
        /// 叶子节点点的个数        /// 
        private int leafnum = 30;        /// 
        /// 待分类数据        /// 
        private List rawData;        /// 
        /// 生成原始数据        /// 
        private void GeneralRawData()        {            if (rawData == null)            {                rawData = new List();            }            else            {                rawData.Clear();            }            Random r = new Random();            for (int i = 0; i < 500; i++)            {                rawData.Add(new Point() { X = r.NextDouble(), Y = r.NextDouble(), Z = r.NextDouble() });            }        }        /// 
        /// 创建KD树        /// 
        ///         ///         private Node CreateKDTree(List data)        {            // 创建根节点            Node root = new Node();            // 添加当前节点数据            root.nodeData = data;            // 如果节点的数据数量小于叶子节点的数量限制，则当前节点为叶子节点            if (data.Count <= leafnum)            {                root.leftNode = null;                root.rightNode = null;                root.point = double.NaN;                root.splitaxis = -1;                return root;            }            // 找到分割轴            int splitAxis = GetSplitAxis(data);            // 分割数据            Tuple, List> dataSplit = GetSplitNum(data, splitAxis);            root.splitaxis = splitAxis;            root.point = dataSplit.Item1;            root.leftNode = CreateKDTree(dataSplit.Item2);            root.rightNode = CreateKDTree(dataSplit.Item3);            return root;        }        private Tuple, List> GetSplitNum(List data, int splitAxis)        {            // 对数据按照第splitAxis排序            var data0 = splitAxis == 0 ? (data.OrderBy(x => x.X)).ToList() :                 (splitAxis == 1 ? (data.OrderBy(x => x.Y)).ToList() :                 (data.OrderBy(x => x.Z)).ToList());            int half = data0.Count / 2;            List leftdata = new List();            List rightdata = new List();            for (int i = 0; i < data0.Count; i++)            {                if (i <= half)                {                    leftdata.Add(data0[i]);                }                else                {                    rightdata.Add(data0[i]);                }            }            double splitnum = splitAxis == 0 ? data[half].X + data[half + 1].X :                (splitAxis == 1 ? data[half].Y + data[half + 1].Y :                data[half].Z + data[half + 1].Z);            return new Tuple, List>(splitnum / 2, leftdata, rightdata);        }        /// 
        /// 获取分割轴编号        /// 
        ///         ///         private int GetSplitAxis(List data)        {            // 设定数据范围最大的轴作为分割轴（也有其他的方式，如方差，或者轮流的方式）            var xData = data.Select(item => item.X);            var yData = data.Select(item => item.Y);            var zData = data.Select(item => item.Z);            List ranges = new List();            ranges.Add(xData.Max() - xData.Min());            ranges.Add(yData.Max() - yData.Min());            ranges.Add(zData.Max() - zData.Min());            var sorted = ranges.Select((x, i) => new KeyValuePair(x, i)).OrderByDescending(x => x.Key).ToList();            return sorted.Select(x => x.Value).ToList()[0]; ;        }        public KNN()        {            GeneralRawData();            Node node = CreateKDTree(rawData);        }    }    /// 
    /// Description of Node.    /// 
    public class Node    {        /// 
        /// 切分的阈值点        /// 
        public double point;        /// 
        /// 左节点        /// 
        public Node leftNode;        /// 
        /// 右节点        /// 
        public Node rightNode;        /// 
        /// 节点包含的数据        /// 
        public List nodeData;        /// 
        /// 分割轴        /// 
        public int splitaxis;        public Node()        {        }    }    public class Point    {        public double X;        public double Y;        public double Z;    }}