计数排序

线性排序

初步代码实现：不稳定排序

/**
 * @Author: subd
 * @Date: 2019/8/26 7:26
 * @descrition 计数排序
 */
public class CountSort {
    public static int[] countSort(int[] array) {
        //1.得到数列的最大值
        int max = array[0];
        for (int i = 0; i < array.length; i++) {
            if (array[i] > max) {
                max = array[i];
            }
        }
        //2.根据数列的最大值确定统计数组的长度
        int[] countArray = new int[max + 1];
        //3.遍历数列，填充统计数组
        for (int i = 0; i < array.length; i++) {
            countArray[array[i]]++;
        }
        //4.遍历统计数组，输出结果
        int index = 0;
        int[] sortedArray = new int[array.length];
        for (int i = 0; i < countArray.length; i++) {
            for (int j = 0; j < countArray[i]; j++) {
                sortedArray[index++] = i;
            }
        }
        return sortedArray;
    }

    public static void main(String[] args) {
        int[] array = new int[]{4, 4, 6, 5, 3, 2, 8, 1, 7, 5, 6, 0, 10};
        int[] sortedArray = countSort(array);
        System.out.println(Arrays.toString(sortedArray));
    }
}

代码实现2：稳定排序

/**
 * @Author: subd
 * @Date: 2019/8/26 7:41
 * @descrition 计数排序
 */
public class CountSort2 {
    public static int[] countSort(int[] array) {
        //1.得到数列的最大值,并计算出差值d
        int max = array[0];
        int min = array[0];
        for (int i = 0; i < array.length; i++) {
            if (array[i] > max) {
                max = array[i];
            }
            if (array[i] < min) {
                min = array[i];
            }
        }
        int d = max - min;
        //2.创建统计数组并对统计对应元素的个数。
        int[] countArray = new int[d + 1];
        for (int i = 0; i < array.length; i++) {
            countArray[array[i] - min]++;
        }
        //3.统计数组做变形，后面的元素等于前面的元素之和
        for (int i = 1; i < countArray.length; i++) {
            countArray[i] += countArray[i - 1];
        }
        //4.倒序遍历原始数列，从统计数组找到正确位置，输出到结果数组
        int[] sortedArray = new int[array.length];
        for (int i = array.length - 1; i >= 0; i--) {
            sortedArray[countArray[array[i] - min] - 1] = array[i];
            countArray[array[i] - min]--;
        }
        return sortedArray;
    }

    public static void main(String[] args) {
        int[] array = new int[]{95,94,91,98,99,90,99,93,91,92};
        int[] sortedArray = countSort(array);
        System.out.println(Arrays.toString(sortedArray));
    }
}