make buckets in java bucket sort code example

Example 1: java bucket sort

public static int[] bucketSort(int[] a) {
  Queue<Integer>[] buckets = fillBuckets(a);
  int[] sorted = readBuckets(buckets);
  return sorted;
}

public static Queue<Integer>[] fillBuckets(int[] array) {
  if(array.length == 0){
    Queue<Integer>[] r = new Queue[0];
    return r;
  }
  int vmin = array[0];
  int vmax = array[0];
  for(int i = 0; i < array.length; i++){
    if(array[i] > vmax){
      vmax = array[i];
    }
    if(array[i] < vmin){
      vmin = array[i];
    }
  }
  Queue<Integer>[] buckets = new Queue[vmax - vmin + 1];
  for(int i = 0; i < buckets.length; i++){
    buckets[i] = new LinkedList<Integer>();
  }
  for(int i = 0; i < array.length; i++){
    buckets[array[i] - vmin].add(array[i]);
  }
  return buckets;
}

public static int[] readBuckets(Queue<Integer>[] buckets) {
  if(buckets.length == 0){
    int[] e = new int[0];
    return e;
  }
  ArrayList<Integer> a = new ArrayList<Integer>();
  for(int i = 0 ; i < buckets.length; i++){
    while(buckets[i].peek() != null){
      a.add(buckets[i].remove());
    }
  }
  int[] result = new int[a.size()];
  for(int i = 0; i < a.size(); i++){
    result[i] = a.get(i);
  }
  return result;
}

Example 2: bucket sort algorithm java

// Bucket sort in Java

import java.util.ArrayList;
import java.util.Collections;

public class BucketSort {
  public void bucketSort(float[] arr, int n) {
    if (n <= 0)
      return;
    @SuppressWarnings("unchecked")
    ArrayList<Float>[] bucket = new ArrayList[n];

    // Create empty buckets
    for (int i = 0; i < n; i++)
      bucket[i] = new ArrayList<Float>();

    // Add elements into the buckets
    for (int i = 0; i < n; i++) {
      int bucketIndex = (int) arr[i] * n;
      bucket[bucketIndex].add(arr[i]);
    }

    // Sort the elements of each bucket
    for (int i = 0; i < n; i++) {
      Collections.sort((bucket[i]));
    }

    // Get the sorted array
    int index = 0;
    for (int i = 0; i < n; i++) {
      for (int j = 0, size = bucket[i].size(); j < size; j++) {
        arr[index++] = bucket[i].get(j);
      }
    }
  }

  // Driver code
  public static void main(String[] args) {
    BucketSort b = new BucketSort();
    float[] arr = { (float) 0.42, (float) 0.32, (float) 0.33, (float) 0.52, (float) 0.37, (float) 0.47,
        (float) 0.51 };
    b.bucketSort(arr, 7);

    for (float i : arr)
      System.out.print(i + "  ");
  }
}