歐式距離

package com.rongyi.platform.game.web.data;

import org.apache.commons.math3.stat.descriptive.moment.StandardDeviation;

import java.util.Arrays;
import java.util.List;


public class EuclideanDistance {

    public static double calculateEuclideanDistance(List<Double> list1, List<Double> list2) {
        // 確保兩個集合的大小相同
        if (list1.size() != list2.size()) {
            throw new IllegalArgumentException("歐式距離集合大小必選相同");
        }

        // 計算歐式距離
        double distanceSquared = 0.0;
        for (int i = 0; i < list1.size(); i++) {
            double temp = Math.pow(list1.get(i) - list2.get(i), 2);
            distanceSquared += temp;

        }
//        return Math.sqrt(distanceSquared);
        return distanceSquared;
    }

    public static double calculateEuclideanDistance2(List<Double> list1, List<Double> list2) {
        // 確保兩個集合的大小相同
        if (list1.size() != list2.size()) {
            throw new IllegalArgumentException("歐式距離集合大小必選相同");
        }

        // 將集合轉換為double數組
        double[] array1 = list1.stream().mapToDouble(Double::doubleValue).toArray();
        double[] array2 = list2.stream().mapToDouble(Double::doubleValue).toArray();

        // 計算歐式距離
        StandardDeviation stdDev = new StandardDeviation();
        double stdDev1 = stdDev.evaluate(array1);
        double stdDev2 = stdDev.evaluate(array2);

        // 標準差的平方就是歐式距離的平方
        double distanceSquared = 0.0;
        for (int i = 0; i < array1.length; i++) {
            distanceSquared += Math.pow(array1[i] - array2[i], 2);
        }
        return Math.sqrt(distanceSquared) / (stdDev1 + stdDev2);
    }
}