refactor: cleanup CocktailShakerSort (#5317)

src/main/java/com/thealgorithms/sorts/CocktailShakerSort.java

@@ -1,57 +1,81 @@
 package com.thealgorithms.sorts;
 
 /**
+ * CocktailShakerSort class implements the Cocktail Shaker Sort algorithm,
+ * which is a bidirectional bubble sort. It sorts the array by passing
+ * through it back and forth, progressively moving the largest elements
+ * to the end and the smallest elements to the beginning.
+ *
  * @author Mateus Bizzo (https://github.com/MattBizzo)
  * @author Podshivalov Nikita (https://github.com/nikitap492)
  */
 class CocktailShakerSort implements SortAlgorithm {
 
     /**
-     * This method implements the Generic Cocktail Shaker Sort
+     * Sorts the given array using the Cocktail Shaker Sort algorithm.
      *
-     * @param array The array to be sorted Sorts the array in increasing order
+     * @param <T> The type of elements in the array, which must be comparable
+     * @param array The array to be sorted
+     * @return The sorted array
      */
     @Override
-    public <T extends Comparable<T>> T[] sort(T[] array) {
-        int length = array.length;
-        int left = 0;
-        int right = length - 1;
-        int swappedLeft;
-        int swappedRight;
-        while (left < right) {
-            // front
-            swappedRight = 0;
-            for (int i = left; i < right; i++) {
-                if (SortUtils.less(array[i + 1], array[i])) {
-                    SortUtils.swap(array, i, i + 1);
-                    swappedRight = i;
-                }
-            }
-            // back
-            right = swappedRight;
-            swappedLeft = length - 1;
-            for (int j = right; j > left; j--) {
-                if (SortUtils.less(array[j], array[j - 1])) {
-                    SortUtils.swap(array, j - 1, j);
-                    swappedLeft = j;
-                }
-            }
-            left = swappedLeft;
+    public <T extends Comparable<T>> T[] sort(final T[] array) {
+        if (array.length == 0) {
+            return array;
         }
+
+        int left = 0;
+        int right = array.length - 1;
+
+        while (left < right) {
+            right = performForwardPass(array, left, right);
+            left = performBackwardPass(array, left, right);
+        }
+
         return array;
     }
 
-    // Driver Program
-    public static void main(String[] args) {
-        // Integer Input
-        Integer[] integers = {4, 23, 6, 78, 1, 54, 231, 9, 12};
-        CocktailShakerSort shakerSort = new CocktailShakerSort();
+    /**
+     * Performs a forward pass through the array, moving larger elements to the end.
+     *
+     * @param <T>   The type of elements in the array, which must be comparable
+     * @param array The array being sorted
+     * @param left  The current left boundary of the sorting area
+     * @param right The current right boundary of the sorting area
+     * @return The index of the last swapped element during this pass
+     */
+    private <T extends Comparable<T>> int performForwardPass(final T[] array, final int left, final int right) {
+        int lastSwappedIndex = left;
 
-        // Output => 1 4 6 9 12 23 54 78 231
-        SortUtils.print(shakerSort.sort(integers));
+        for (int i = left; i < right; i++) {
+            if (SortUtils.less(array[i + 1], array[i])) {
+                SortUtils.swap(array, i, i + 1);
+                lastSwappedIndex = i;
+            }
+        }
 
-        // String Input
-        String[] strings = {"c", "a", "e", "b", "d"};
-        SortUtils.print(shakerSort.sort(strings));
+        return lastSwappedIndex;
+    }
+
+    /**
+     * Performs a backward pass through the array, moving smaller elements to the beginning.
+     *
+     * @param <T>   The type of elements in the array, which must be comparable
+     * @param array The array being sorted
+     * @param left  The current left boundary of the sorting area
+     * @param right The current right boundary of the sorting area
+     * @return The index of the last swapped element during this pass
+     */
+    private <T extends Comparable<T>> int performBackwardPass(final T[] array, final int left, final int right) {
+        int lastSwappedIndex = right;
+
+        for (int i = right; i > left; i--) {
+            if (SortUtils.less(array[i], array[i - 1])) {
+                SortUtils.swap(array, i - 1, i);
+                lastSwappedIndex = i;
+            }
+        }
+
+        return lastSwappedIndex;
     }
 }