1+ /**
2+ * Bucket sort implementation
3+ *
4+ *
5+ * @author William Fiset, william.alexandre.fiset@gmail.com
6+ */
7+ 8+ package Sorting ;
9+ 10+ import java .util .*;
11+ 12+ public class BucketSort {
13+ // Performs a bucket sort of an array in which all the elements are
14+ // bounded in the range [minValue, maxValue]. For bucket sort to give linear
15+ // performance the elements need to be uniformly distributed
16+ private static void bucketSort (int [] ar ) {
17+ 18+ if (ar == null || ar .length == 0 ) return ;
19+ 20+ int minValue = Integer .MAX_VALUE ;
21+ int maxValue = Integer .MIN_VALUE ;
22+ for (int i = 0 ; i < ar .length ; i ++) {
23+ if (ar [i ] < minValue ) minValue = ar [i ];
24+ if (ar [i ] > maxValue ) maxValue = ar [i ];
25+ }
26+ if (minValue == maxValue ) return ;
27+ 28+ // N is number elements and M is the range of values
29+ final int N = ar .length , M = maxValue - minValue + 1 , numBuckets = M / N + 1 ;
30+ List <List <Integer >> buckets = new ArrayList <>(numBuckets );
31+ for (int i = 0 ; i < numBuckets ; i ++) buckets .add (new ArrayList <>());
32+ 33+ // Place each element in a bucket
34+ for (int i = 0 ; i < N ; i ++) {
35+ int bi = (ar [i ] - minValue ) / M ;
36+ List <Integer > bucket = buckets .get (bi );
37+ bucket .add (ar [i ]);
38+ }
39+ 40+ // Sort buckets and stitch together answer
41+ for (int bi = 0 , j = 0 ; bi < numBuckets ; bi ++) {
42+ List <Integer > bucket = buckets .get (bi );
43+ if (bucket != null ) {
44+ Collections .sort (bucket );
45+ for (int k = 0 ; k < bucket .size (); k ++) {
46+ ar [j ++] = bucket .get (k );
47+ }
48+ }
49+ }
50+ }
51+ 52+ public static void main (String [] args ) {
53+ 54+ int [] array = {10 , 4 , 6 , 8 , 13 , 2 , 3 };
55+ BucketSort .bucketSort (array );
56+ // Prints:
57+ // [2, 3, 4, 6, 8, 10, 13]
58+ System .out .println (java .util .Arrays .toString (array ));
59+ 60+ array = new int [] {10 , 10 , 10 , 10 , 10 };
61+ BucketSort .bucketSort (array );
62+ // Prints:
63+ // [10, 10, 10, 10, 10]
64+ System .out .println (java .util .Arrays .toString (array ));
65+ }
66+ }
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