/**  * KNN算法工具类  * Created by Mistletoe on 2018/05/11 17:13  */  import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;  public class KNNUtils {

    private static double[] originData;
    public void init(double[] outData){
        this.originData=outData;
    }
    public KNNUtils(double[] outData){
        init(outData);
    }
    //计算欧氏距离
    private  double calEulaDistance(double centerPoint,double point){
        return Math.sqrt((centerPoint-point)*(centerPoint-point));
    }
    //计算一个随机长度集合元素的均值
    private  double calAverage2GetCenterPoint(List<Double> group) {
        int sum=0;
        for(int i=0;i< group.size();i++){
            sum+=group.get(i);
        }
        return sum/group.size();
    }
    //KNN算法迭代器
    public  Map<Integer,List<Double>> devide(Map<Integer,List<Double>> myMap,double[] centerPoints){
        int blockNum=myMap.size();
        Map<Integer,List<Double>> newMap=new HashMap<>();
        for(int i=0;i<blockNum;i++){
            newMap.put(i,new ArrayList<>());
        }
        boolean loopFlag=true;
        //聚类算法原理:https://blog.csdn.net/zhangphil/article/details/78783629
        do {
            double minNum = Double.MAX_VALUE;
            int keyPosition = -1;
            for (int j = 0; j < originData.length; j++) {

                for (int i = 0; i < blockNum; i++) {
                    double ret = calEulaDistance(centerPoints[i], originData[j]);
                    if (ret < minNum) {
                        keyPosition += 1;
                        minNum = ret;
                    }
                }
                newMap.get(keyPosition).add(originData[j]);
                if(keyPosition>newMap.size()) {
                    keyPosition = -1;
                }
            }
            int equalsNum = 0;
            double[] newCenterPoints = new double[centerPoints.length];
            for (int i = 0; i < blockNum; i++) {
                newCenterPoints[i] = calAverage2GetCenterPoint(newMap.get(i));
            }
            //当前聚类精度设置为0.01;
            for (int i = 0; i < centerPoints.length; i++) {
                if (Math.abs(newCenterPoints[i]-centerPoints[i])<0.01) {
                    equalsNum += 1;
                }
            }
            if (equalsNum == centerPoints.length) {
               loopFlag=false;
            }else{
                for(int i=0;i<centerPoints.length;i++) {
                    centerPoints[i] = newCenterPoints[i];
                    //上一轮map清空
                    newMap.get(i).clear();
                }
            }
        }while (loopFlag);
        return newMap;
    }
}