Add TournamentSort sorting algorithm (#6631)

Author: eswarseeram

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

@@ -0,0 +1,61 @@
+package com.thealgorithms.sorts;
+
+import java.util.Arrays;
+
+public class TournamentSort implements SortAlgorithm {
+
+    @Override
+    public <T extends Comparable<T>> T[] sort(T[] array) {
+        if (array == null || array.length <= 1) return array;
+        T[] arr = Arrays.copyOf(array, array.length);
+        int n = arr.length;
+        T[] sorted = Arrays.copyOf(array, array.length);
+
+        for (int i = 0; i < n; i++) {
+            int size = nextPowerOfTwo(n - i);
+            @SuppressWarnings("unchecked")
+            T[] tree = (T[]) new Comparable[2 * size - 1];
+            for (int j = 0; j < n - i; j++) tree[size - 1 + j] = arr[j];
+            for (int j = size - 2; j >= 0; j--) {
+                T left = tree[2 * j + 1], right = tree[2 * j + 2];
+                if (left == null) tree[j] = right;
+                else if (right == null) tree[j] = left;
+                else tree[j] = left.compareTo(right) <= 0 ? left : right;
+            }
+            sorted[i] = tree[0];
+            removeWinner(arr, sorted[i]);
+        }
+        return sorted;
+    }
+
+    private <T extends Comparable<T>> void removeWinner(T[] arr, T winner) {
+        for (int i = 0; i < arr.length; i++) {
+            if (arr[i] != null && arr[i].equals(winner)) {
+                arr[i] = null;
+                compact(arr);
+                break;
+            }
+        }
+    }
+
+    private <T> void compact(T[] arr) {
+        int index = 0;
+        for (T element : arr) {
+            if (element != null) arr[index++] = element;
+        }
+        while (index < arr.length) arr[index++] = null;
+    }
+
+    private int nextPowerOfTwo(int n) {
+        int p = 1;
+        while (p < n) p <<= 1;
+        return p;
+    }
+
+    public static void main(String[] args) {
+        TournamentSort sorter = new TournamentSort();
+        Integer[] arr = {5, 3, 8, 4, 1, 2};
+        Integer[] res = sorter.sort(arr);
+        System.out.println(Arrays.toString(res));
+    }
+}

src/test/java/com/thealgorithms/sorts/TournamentSortTest.java

@@ -0,0 +1,44 @@
+package com.thealgorithms.sorts;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+public class TournamentSortTest {
+
+    @Test
+    public void testBasic() {
+        TournamentSort sorter = new TournamentSort();
+        Integer[] arr = {5, 3, 8, 4, 1, 2};
+        Integer[] expected = {1, 2, 3, 4, 5, 8};
+        assertArrayEquals(expected, sorter.sort(arr));
+    }
+
+    @Test
+    public void testAlreadySorted() {
+        TournamentSort sorter = new TournamentSort();
+        Integer[] arr = {1, 2, 3, 4};
+        assertArrayEquals(arr, sorter.sort(arr));
+    }
+
+    @Test
+    public void testReverseOrder() {
+        TournamentSort sorter = new TournamentSort();
+        Integer[] arr = {9, 7, 5, 3, 1};
+        Integer[] expected = {1, 3, 5, 7, 9};
+        assertArrayEquals(expected, sorter.sort(arr));
+    }
+
+    @Test
+    public void testSingleElement() {
+        TournamentSort sorter = new TournamentSort();
+        Integer[] arr = {42};
+        assertArrayEquals(arr, sorter.sort(arr));
+    }
+
+    @Test
+    public void testEmptyArray() {
+        TournamentSort sorter = new TournamentSort();
+        Integer[] arr = {};
+        assertArrayEquals(arr, sorter.sort(arr));
+    }
+}