Merge pull request #70 from gabrielfernans/master

Add BucketSort java

Sorting/BucketSort.java

@@ -0,0 +1,73 @@
+/**
+ * BucketSort: mainly sort an array with elements uniformly distributed over a range.
+ *
+ * Worst Case Time Complexity: O(n^2).
+ * Best and Average Case Time Complexity: O(n + k).
+ * Space Complexity: O(n * k).
+ *
+ */
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.ArrayList;
+
+/**
+ * http://www.growingwiththeweb.com/2015/06/bucket-sort.html
+ */
+public class BucketSort {
+
+    private static final int DEFAULT_BUCKET_SIZE = 5;
+
+    public static void sort(int[] arr) {
+        bucketSort(arr, DEFAULT_BUCKET_SIZE);
+    }
+
+    public static void bucketSort(int arr[], int size) {
+        if (arr.length == 0) return;
+
+        Integer minValue = arr[0];
+        Integer maxValue = arr[0];
+        for (int i = 1; i < arr.length; i++) {
+            if (arr[i] < minValue) {
+                minValue = arr[i];
+            } else if (arr[i] > maxValue) {
+                maxValue = arr[i];
+            }
+        }
+
+        int bucketCount = (maxValue - minValue) / size + 1;
+        List<List<Integer>> buckets = new ArrayList<List<Integer>>(bucketCount);
+        for (int i = 0; i < bucketCount; i++) {
+            buckets.add(new ArrayList<Integer>());
+        }
+
+        for (int i = 0; i < arr.length; i++) {
+            buckets.get((arr[i] - minValue) / size).add(arr[i]);
+        }
+
+        int currentIndex = 0;
+        for (int i = 0; i < buckets.size(); i++) {
+            Integer[] bucketArray = new Integer[buckets.get(i).size()];
+            bucketArray = buckets.get(i).toArray(bucketArray);
+            InsertionSort.sort(bucketArray);
+            for (int j = 0; j < bucketArray.length; j++) {
+                arr[currentIndex++] = bucketArray[j];
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        int[] arr1 = {10, 3, 7, 5, 1, 15, 20};
+        BucketSort.sort(arr1);
+        System.out.println(Arrays.toString(arr1));
+
+        int[] arr2 = {};
+        BucketSort.sort(arr2);
+        System.out.println(Arrays.toString(arr2));
+
+        int[] arr3 = {10};
+        BucketSort.sort(arr3);
+        System.out.println(Arrays.toString(arr3));
+    }
+
+}