对于一个int数组，请编写一个计数排序算法，对数组元素排序。
给定一个int数组A及数组的大小n，请返回排序后的数组。

测试样例：

[1,2,3,5,2,3],6
[1,2,2,3,3,5]
我的提交

-- coding:utf-8 --

class CountingSort:
def countingSort(self, A, n):

write code here

    seta = set(A)
    minnum = min(seta)
    maxnum = max(seta)
    buckets = {}
    for i in range(minnum, maxnum+1):
        buckets[i] = 0

    for num in range(n):
        buckets[A[num]] = buckets[A[num]] + 1

    B = []
    for j in range(minnum, maxnum+1):
        B.extend([j] * buckets[j])
    return B

if name == 'main':
c = CountingSort()
print(c.countingSort([54,35,48,36,27,12,44,44,8,14,26,17,28],13))
调整一下，减少空间消耗

-- coding:utf-8 --

class CountingSort:
def countingSort(self, A, n):

write code here

    seta = set(A)
    minnum = min(seta)
    maxnum = max(seta)
    buckets = {}
    for i in range(minnum, maxnum+1):
        buckets[i] = 0

    for num in range(n):
        buckets[A[num]] = buckets[A[num]] + 1

    i = 0
    for j in range(minnum, maxnum+1):
        for _ in range(buckets[j]):
            A[i] = j
            i += 1
    return A

if name == 'main':
c = CountingSort()
print(c.countingSort([54,35,48,36,27,12,44,44,8,14,26,17,28],13))
参考答案
public class CountSort {

public static void countSort(int[] arr) {
    if (arr == null || arr.length < 2) {
        return;
    }
    int min = arr[0];
    int max = arr[0];
    for (int i = 1; i < arr.length; i++) {
        min = Math.min(arr[i], min);
        max = Math.max(arr[i], max);
    }
    int[] countArr = new int[max - min + 1];
    for (int i = 0; i < arr.length; i++) {
        countArr[arr[i] - min]++;
    }
    int index = 0;
    for (int i = 0; i < countArr.length; i++) {
        while (countArr[i]-- > 0) {
            arr[index++] = i + min;
        }
    }
}

public static void swap(int[] arr, int index1, int index2) {
    int tmp = arr[index1];
    arr[index1] = arr[index2];
    arr[index2] = tmp;
}

public static int[] generateArray(int len, int range) {
    if (len < 1) {
        return null;
    }
    int[] arr = new int[len];
    for (int i = 0; i < len; i++) {
        arr[i] = (int) (Math.random() * range);
    }
    return arr;
}

public static void printArray(int[] arr) {
    if (arr == null || arr.length == 0) {
        return;
    }
    for (int i = 0; i < arr.length; i++) {
        System.out.print(arr[i] + " ");
    }
    System.out.println();
}

public static boolean isSorted(int[] arr) {
    if (arr == null || arr.length < 2) {
        return true;
    }
    for (int i = 1; i < arr.length; i++) {
        if (arr[i - 1] > arr[i]) {
            return false;
        }
    }
    return true;
}

public static void main(String[] args) {
    int len = 10;
    int range = 10;
    int testTimes = 50000;
    for (int i = 0; i < testTimes; i++) {
        int[] arr = generateArray(len, range);
        countSort(arr);
        if (!isSorted(arr)) {
            System.out.println("Wrong Case:");
            printArray(arr);
            break;
        }
    }

    int len2 = 13;
    int range2 = 10;
    int testTimes2 = 50000;
    for (int i = 0; i < testTimes2; i++) {
        int[] arr = generateArray(len2, range2);
        countSort(arr);
        if (!isSorted(arr)) {
            System.out.println("Wrong Case:");
            printArray(arr);
            break;
        }
    }
}

}