Bucket sort

Bucket sorting is a sorting algorithm that works with partitioning an array into a number of packets. Each bucket sorted individually using the same or different algorithm. Bucket sort and radix sort look like same. But it has some difference.

The following table shows the difference between Bucket sort and radix sort.

Write a program to implement bucket sort algorithm.

source Code

package com.dsacode.Algorithm.sorting;
 
import java.util.Arrays;
 
public class Bucketsort {
 
     public static int[] bucketSort(int[] arr) {
            int i, j;
            int[] count = new int[arr.length];
            Arrays.fill(count, 0);
 
            for (i = 0; i < arr.length; i++) {
                count[arr[i]]++;
            }
 
            for (i = 0, j = 0; i < count.length; i++) {
                for (; count[i]>0; (count[i])--) {
                    arr[j++] = i;
                }
            }
            return arr;
        }
 
        public static void main(String[] args) {
             
            int[] arr = new int[] { 1, 3, 4, 6, 4, 2, 9, 1, 2, 9 };
          
            System.out.println("unsorted array before sorting : " + Arrays.toString(arr));
          
            arr = bucketSort(arr);
          
            System.out.println("Sorted array After bucketSort sorting : " + Arrays.toString(arr));
        }
}

Output

Unsorted array before sorting: [1, 3, 4, 6, 4, 2, 9, 1, 2, 9]
Sorted array after bucket Sort sorting: [1, 1, 2, 2, 3, 4, 4, 6, 9, 9]

Algorithm Explanation

	Send the unsorted array to utility function and find its max value.
	Bucket size should be maxed Value + 1 since index of array starts from 0.
	Distribute the array element into bucket
	Walk through bucket from the start and pull the bucket element which should be already sorted.

Time Complexity

Reference

1. https://en.wikipedia.org/wiki/Bucket_sort
2. https://www.cs.usfca.edu/~galles/visualization/BucketSort.html