refactor: simple improvements and cleanup for different sorts (#5318)

Author: alxkm

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])) {

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

@@ -25,9 +25,9 @@ public <T extends Comparable<T>> T[] sort(T[] array) {
      * @param right The last index of an array
      * @param array The array to be sorted
      */
-    private static <T extends Comparable<T>> void doSort(T[] array, int left, int right) {
+    private static <T extends Comparable<T>> void doSort(T[] array, final int left, final int right) {
         if (left < right) {
-            int pivot = randomPartition(array, left, right);
+            final int pivot = randomPartition(array, left, right);
             doSort(array, left, pivot - 1);
             doSort(array, pivot, right);
         }
@@ -41,8 +41,8 @@ private static <T extends Comparable<T>> void doSort(T[] array, int left, int ri
      * @param right The last index of an array
      * @return the partition index of the array
      */
-    private static <T extends Comparable<T>> int randomPartition(T[] array, int left, int right) {
-        int randomIndex = left + (int) (Math.random() * (right - left + 1));
+    private static <T extends Comparable<T>> int randomPartition(T[] array, final int left, final int right) {
+        final int randomIndex = left + (int) (Math.random() * (right - left + 1));
         SortUtils.swap(array, randomIndex, right);
         return partition(array, left, right);
     }
@@ -56,8 +56,8 @@ private static <T extends Comparable<T>> int randomPartition(T[] array, int left
      * array
      */
     private static <T extends Comparable<T>> int partition(T[] array, int left, int right) {
-        int mid = (left + right) >>> 1;
-        T pivot = array[mid];
+        final int mid = (left + right) >>> 1;
+        final T pivot = array[mid];
 
         while (left <= right) {
             while (SortUtils.less(array[left], pivot)) {

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

@@ -27,7 +27,7 @@ public <T extends Comparable<T>> T[] sort(T[] array) {
      * @param index the current index to start sorting from
      * @param <T>   the type of elements in the array (must be Comparable)
      */
-    private static <T extends Comparable<T>> void recursiveSelectionSort(T[] array, int index) {
+    private static <T extends Comparable<T>> void recursiveSelectionSort(T[] array, final int index) {
         if (index == array.length - 1) {
             return;
         }
@@ -46,7 +46,7 @@ private static <T extends Comparable<T>> void recursiveSelectionSort(T[] array,
      * @param <T>   the type of elements in the array
      * @return the index of the minimum element
      */
-    private static <T extends Comparable<T>> int findMinIndex(T[] array, int start) {
+    private static <T extends Comparable<T>> int findMinIndex(T[] array, final int start) {
         // Base case: if start is the last index, return start
         if (start == array.length - 1) {
             return start;

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

@@ -15,20 +15,20 @@ public <T extends Comparable<T>> T[] sort(T[] array) {
         return array;
     }
 
-    public <T extends Comparable<T>> T[] sort(T[] unsortedArray, int start, int end) {
-        if (SortUtils.less(unsortedArray[end - 1], unsortedArray[start])) {
-            T temp = unsortedArray[start];
-            unsortedArray[start] = unsortedArray[end - 1];
-            unsortedArray[end - 1] = temp;
+    public <T extends Comparable<T>> T[] sort(final T[] array, final int start, final int end) {
+        if (SortUtils.less(array[end - 1], array[start])) {
+            final T temp = array[start];
+            array[start] = array[end - 1];
+            array[end - 1] = temp;
         }
 
-        int len = end - start;
-        if (len > 2) {
-            int third = len / 3;
-            sort(unsortedArray, start, end - third);
-            sort(unsortedArray, start + third, end);
-            sort(unsortedArray, start, end - third);
+        final int length = end - start;
+        if (length > 2) {
+            int third = length / 3;
+            sort(array, start, end - third);
+            sort(array, start + third, end);
+            sort(array, start, end - third);
         }
-        return unsortedArray;
+        return array;
     }
 }

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

@@ -13,14 +13,14 @@ public final class StrandSort implements SortAlgorithm {
      * Sorts the given array using the Strand Sort algorithm.
      *
      * @param <T> The type of elements to be sorted, must be Comparable.
-     * @param unsorted The array to be sorted.
+     * @param array The array to be sorted.
      * @return The sorted array.
      */
     @Override
-    public <T extends Comparable<T>> T[] sort(T[] unsorted) {
-        List<T> unsortedList = new ArrayList<>(Arrays.asList(unsorted));
+    public <T extends Comparable<T>> T[] sort(T[] array) {
+        List<T> unsortedList = new ArrayList<>(Arrays.asList(array));
         List<T> sortedList = strandSort(unsortedList);
-        return sortedList.toArray(unsorted);
+        return sortedList.toArray(array);
     }
 
     /**

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

@@ -11,11 +11,10 @@ public class SwapSort implements SortAlgorithm {
 
     @Override
     public <T extends Comparable<T>> T[] sort(T[] array) {
-        int len = array.length;
         int index = 0;
 
-        while (index < len - 1) {
-            int amountSmallerElements = this.getSmallerElementCount(array, index);
+        while (index < array.length - 1) {
+            final int amountSmallerElements = this.getSmallerElementCount(array, index);
 
             if (amountSmallerElements > 0) {
                 SortUtils.swap(array, index, index + amountSmallerElements);
@@ -27,7 +26,7 @@ public <T extends Comparable<T>> T[] sort(T[] array) {
         return array;
     }
 
-    private <T extends Comparable<T>> int getSmallerElementCount(T[] array, int index) {
+    private <T extends Comparable<T>> int getSmallerElementCount(final T[] array, final int index) {
         int counter = 0;
         for (int i = index + 1; i < array.length; i++) {
             if (SortUtils.less(array[i], array[index])) {

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

@@ -12,25 +12,25 @@ class TimSort implements SortAlgorithm {
     private Comparable[] aux;
 
     @Override
-    public <T extends Comparable<T>> T[] sort(T[] a) {
-        int n = a.length;
+    public <T extends Comparable<T>> T[] sort(T[] array) {
+        final int n = array.length;
 
         InsertionSort insertionSort = new InsertionSort();
         for (int i = 0; i < n; i += SUB_ARRAY_SIZE) {
-            insertionSort.sort(a, i, Math.min(i + SUB_ARRAY_SIZE, n));
+            insertionSort.sort(array, i, Math.min(i + SUB_ARRAY_SIZE, n));
         }
 
         aux = new Comparable[n];
         for (int sz = SUB_ARRAY_SIZE; sz < n; sz = sz + sz) {
             for (int lo = 0; lo < n - sz; lo += sz + sz) {
-                merge(a, lo, lo + sz - 1, Math.min(lo + sz + sz - 1, n - 1));
+                merge(array, lo, lo + sz - 1, Math.min(lo + sz + sz - 1, n - 1));
             }
         }
 
-        return a;
+        return array;
     }
 
-    private <T extends Comparable<T>> void merge(T[] a, int lo, int mid, int hi) {
+    private <T extends Comparable<T>> void merge(T[] a, final int lo, final int mid, final int hi) {
         int i = lo;
         int j = mid + 1;
         System.arraycopy(a, lo, aux, lo, hi + 1 - lo);