Merge branch 'master' into refactor/dualpivotquicksort

Author: alxkm

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;
+    public <T extends Comparable<T>> T[] sort(final T[] array) {
+        if (array.length == 0) {
+            return array;
+        }
+
         int left = 0;
-        int right = length - 1;
-        int swappedLeft;
-        int swappedRight;
+        int right = array.length - 1;
+
         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;
+            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;
+
+        for (int i = left; i < right; i++) {
+            if (SortUtils.less(array[i + 1], array[i])) {
+                SortUtils.swap(array, i, i + 1);
+                lastSwappedIndex = i;
+            }
+        }
+
+        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;
 
-        // Output => 1 4 6 9 12 23 54 78 231
-        SortUtils.print(shakerSort.sort(integers));
+        for (int i = right; i > left; i--) {
+            if (SortUtils.less(array[i], array[i - 1])) {
+                SortUtils.swap(array, i - 1, i);
+                lastSwappedIndex = i;
+            }
+        }
 
-        // String Input
-        String[] strings = {"c", "a", "e", "b", "d"};
-        SortUtils.print(shakerSort.sort(strings));
+        return lastSwappedIndex;
     }
 }

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

@@ -12,31 +12,31 @@
 public class DutchNationalFlagSort implements SortAlgorithm {
 
     @Override
-    public <T extends Comparable<T>> T[] sort(T[] unsorted) {
-        return dutchNationalFlagSort(unsorted, unsorted[(int) Math.ceil((unsorted.length) / 2.0) - 1]);
+    public <T extends Comparable<T>> T[] sort(T[] array) {
+        return dutchNationalFlagSort(array, array[(int) Math.ceil((array.length) / 2.0) - 1]);
     }
 
-    public <T extends Comparable<T>> T[] sort(T[] unsorted, T intendedMiddle) {
-        return dutchNationalFlagSort(unsorted, intendedMiddle);
+    public <T extends Comparable<T>> T[] sort(T[] array, T intendedMiddle) {
+        return dutchNationalFlagSort(array, intendedMiddle);
     }
 
-    private <T extends Comparable<T>> T[] dutchNationalFlagSort(T[] arr, T intendedMiddle) {
+    private <T extends Comparable<T>> T[] dutchNationalFlagSort(final T[] array, final T intendedMiddle) {
         int i = 0;
         int j = 0;
-        int k = arr.length - 1;
+        int k = array.length - 1;
 
         while (j <= k) {
-            if (0 > arr[j].compareTo(intendedMiddle)) {
-                SortUtils.swap(arr, i, j);
+            if (0 > array[j].compareTo(intendedMiddle)) {
+                SortUtils.swap(array, i, j);
                 j++;
                 i++;
-            } else if (0 < arr[j].compareTo(intendedMiddle)) {
-                SortUtils.swap(arr, j, k);
+            } else if (0 < array[j].compareTo(intendedMiddle)) {
+                SortUtils.swap(array, j, k);
                 k--;
             } else {
                 j++;
             }
         }
-        return arr;
+        return array;
     }
 }

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

@@ -9,63 +9,20 @@
 public class GnomeSort implements SortAlgorithm {
 
     @Override
-    public <T extends Comparable<T>> T[] sort(T[] arr) {
+    public <T extends Comparable<T>> T[] sort(final T[] array) {
         int i = 1;
         int j = 2;
-        while (i < arr.length) {
-            if (SortUtils.less(arr[i - 1], arr[i])) {
+        while (i < array.length) {
+            if (SortUtils.less(array[i - 1], array[i])) {
                 i = j++;
             } else {
-                SortUtils.swap(arr, i - 1, i);
+                SortUtils.swap(array, i - 1, i);
                 if (--i == 0) {
                     i = j++;
                 }
             }
         }
 
-        return null;
-    }
-
-    public static void main(String[] args) {
-        Integer[] integers = {
-            4,
-            23,
-            6,
-            78,
-            1,
-            26,
-            11,
-            23,
-            0,
-            -6,
-            3,
-            54,
-            231,
-            9,
-            12,
-        };
-        String[] strings = {
-            "c",
-            "a",
-            "e",
-            "b",
-            "d",
-            "dd",
-            "da",
-            "zz",
-            "AA",
-            "aa",
-            "aB",
-            "Hb",
-            "Z",
-        };
-        GnomeSort gnomeSort = new GnomeSort();
-
-        gnomeSort.sort(integers);
-        gnomeSort.sort(strings);
-
-        System.out.println("After sort : ");
-        SortUtils.print(integers);
-        SortUtils.print(strings);
+        return array;
     }
 }

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

@@ -25,13 +25,13 @@ public <T extends Comparable<T>> T[] sort(T[] array) {
         return array;
     }
 
-    private static <T extends Comparable<T>> void heapify(T[] array, int n) {
+    private <T extends Comparable<T>> void heapify(final T[] array, final int n) {
         for (int k = n / 2; k >= 1; k--) {
             siftDown(array, k, n);
         }
     }
 
-    private static <T extends Comparable<T>> void siftDown(T[] array, int k, int n) {
+    private <T extends Comparable<T>> void siftDown(final T[] array, int k, final int n) {
         while (2 * k <= n) {
             int j = 2 * k;
             if (j < n && SortUtils.less(array[j - 1], array[j])) {