桶排序

桶排序是一种线性时间的排序算法。类似于计数排序所创建的统计数组，桶排序需要创建若干个桶来协助排序。

代码示例：

/**
 * @Author: subd
 * @Date: 2019/8/27 7:29
 * 桶排序
 */
public class BuketSort {
    public static void main(String[] args) {
        double[] array = {4.12, 6.421, 0.0023, 3.0, 2.123, 8.122, 4.12, 10.09};
        double[] sortedArray = bucketSort(array);
        System.out.println(Arrays.toString(sortedArray));
    }

    private static double[] bucketSort(double[] array) {
        //1.得到数列的最大值和最小值，并计算出差值d。
        double max = array[0];
        double min = array[0];
        for (int i = 1; i < array.length; i++) {
            if (array[i] > max) {
                max = array[i];
            }
            if (array[i] < min) {
                min = array[i];
            }

        }
        double d = max - min;
        //2.初始化桶
        int bucketNum = array.length;
        ArrayList<LinkedList<Double>> bucketList = new ArrayList<>(bucketNum);
        for (int i = 0; i < bucketNum; i++) {
            bucketList.add(new LinkedList<Double>());
        }
        //3.遍历原始数组，将每个元素放入桶中
        for (int i = 0; i < array.length; i++) {
            int num = (int) ((array[i] - min) * (bucketNum - 1) / d);
            bucketList.get(num).add(array[i]);
        }
        //4.对每个桶内进行排序
        for (int i = 0; i < array.length; i++) {
            //JDK底层采用了归并排序或归并的优化版本
            Collections.sort(bucketList.get(i));
        }
        //5.输出全部元素
        double[] sortedArray = new double[array.length];
        int index = 0;
        for (LinkedList<Double> list : bucketList) {
            for (double element : list) {
                sortedArray[index] = element;
                index++;
            }
        }
        return sortedArray;
    }
}