optimization

Author: realDuYuanChao

Sorts/ShellSort.java

@@ -2,48 +2,40 @@
 
 import static Sorts.SortUtils.*;
 
-
-/**
- * @author dpunosevac
- * @author Podshivalov Nikita (https://github.com/nikitap492)
- * @see SortAlgorithm
- */
 public class ShellSort implements SortAlgorithm {
 
     /**
      * This method implements Generic Shell Sort.
      *
-     * @param array The array to be sorted
+     * @param array the array to be sorted
      */
     @Override
     public <T extends Comparable<T>> T[] sort(T[] array) {
-        int N = array.length;
-        int h = 1;
+        int length = array.length;
+        int gap = 1;
 
-        while (h < N / 3) {
-            h = 3 * h + 1;
+        /* Calculate gap for optimization purpose */
+        while (gap < length / 3) {
+            gap = 3 * gap + 1;
         }
 
-        while (h >= 1) {
-            for (int i = h; i < N; i++) {
-                for (int j = i; j >= h && less(array[j], array[j - h]); j -= h) {
-                    swap(array, j, j - h);
+        for (; gap > 0; gap /= 3) {
+            for (int i = gap; i < length; i++) {
+                int j;
+                for (j = i; j >= gap && less(array[j], array[j - gap]); j -= gap) {
+                    array[j] = array[j - gap];
                 }
+                array[j] = array[i];
             }
-
-            h /= 3;
         }
-
         return array;
     }
 
+    /* Driver Code */
     public static void main(String[] args) {
         Integer[] toSort = {4, 23, 6, 78, 1, 54, 231, 9, 12};
 
         ShellSort sort = new ShellSort();
-        Integer[] sorted = sort.sort(toSort);
-
-        print(sorted);
-
+        print(sort.sort(toSort));
     }
 }