如何按降序对桶排序

Question

请帮帮我，我真的想不通。我刚刚在网上发现了这个关于bucket排序的代码，想知道它是否可以按降序排序？我试着用reverse((，但它似乎不起作用——它仍然是升序。

import java.util.*;
public class BucketSort {
public static void main(String[] args) {
int[] intArr = {47, 85, 10, 45, 16, 34, 67, 80, 34, 4, 0, 99};
//int[] intArr = {21,11,33,70,5,25,65,55};
System.out.println("Original array- " + Arrays.toString(intArr));
bucketSort(intArr, 10);
System.out.println("Sorted array after bucket sort- " + Arrays.toString(intArr));
}

private static void bucketSort(int[] intArr, int noOfBuckets){
// Create bucket array
List<Integer>[] buckets = new List[noOfBuckets];
// Associate a list with each index 
// in the bucket array         
for(int i = 0; i < noOfBuckets; i++){
buckets[i] = new LinkedList<>();
}
// Assign numbers from array to the proper bucket
// by using hashing function
for(int num : intArr){
//System.out.println("hash- " + hash(num));
buckets[hash(num)].add(num);
}
// sort buckets
for(List<Integer> bucket : buckets){
Collections.sort(bucket);
}

int i = 0;
// Merge buckets to get sorted array
for(List<Integer> bucket : buckets){
for(int num : bucket){
intArr[i++] = num;
}
}
}

// A very simple hash function
private static int hash(int num){
return num/10;
}
} 

Answer 1

由于在对Collection进行排序时没有通过比较器，因此默认情况下按升序执行排序。

import java.util.*;
public class BucketSort {
public static void main(String[] args) {
int[] intArr = { 47, 85, 10, 45, 16, 34, 67, 80, 34, 4, 0, 99 };
// int[] intArr = {21,11,33,70,5,25,65,55};
System.out.println("Original array- " + Arrays.toString(intArr));
bucketSort(intArr, 10);
System.out.println("Sorted array after bucket sort- " + Arrays.toString(intArr));
}
private static void bucketSort(int[] intArr, int noOfBuckets) {
// Create bucket array
List<Integer>[] buckets = new List[noOfBuckets];
// Associate a list with each index
// in the bucket array
for (int i = 0; i < noOfBuckets; i++) {
buckets[i] = new LinkedList<>();
}
// Assign numbers from array to the proper bucket
// by using hashing function
for (int num : intArr) {
// System.out.println("hash- " + hash(num));
buckets[hash(num)].add(num);
}
// sort buckets
for (List<Integer> bucket : buckets) {
Collections.sort(bucket, Collections.reverseOrder());
}
int i = 0;
// Merge buckets to get sorted array

for(int j = buckets.length - 1; j >= 0; j--){
for (int num : buckets[j]) {
intArr[i++] = num;
}
}
}
// A very simple hash function
private static int hash(int num) {
return num / 10;
}
}