Added tests for optimised approach

Author: Nandini-Pandey

src/test/java/com/thealgorithms/misc/PalindromeSinglyLinkedListTest.java

@@ -7,6 +7,8 @@
 import org.junit.jupiter.api.Test;
 
 public class PalindromeSinglyLinkedListTest {
+
+    // Stack-based tests
     @Test
     public void testWithEmptyList() {
         assertTrue(PalindromeSinglyLinkedList.isPalindrome(new SinglyLinkedList()));
@@ -67,4 +69,74 @@ public void testWithListWithEvenLengthNegative() {
         exampleList.insert(20);
         assertFalse(PalindromeSinglyLinkedList.isPalindrome(exampleList));
     }
+
+    // Optimized approach tests
+    @Test
+    public void testOptimisedWithEmptyList() {
+        assertTrue(PalindromeSinglyLinkedList.isPalindromeOptimised(null));
+    }
+
+    @Test
+    public void testOptimisedWithSingleElement() {
+        PalindromeSinglyLinkedList.Node node = new PalindromeSinglyLinkedList.Node(100);
+        assertTrue(PalindromeSinglyLinkedList.isPalindromeOptimised(node));
+    }
+
+    @Test
+    public void testOptimisedWithOddLengthPositive() {
+        PalindromeSinglyLinkedList.Node node1 = new PalindromeSinglyLinkedList.Node(1);
+        PalindromeSinglyLinkedList.Node node2 = new PalindromeSinglyLinkedList.Node(2);
+        PalindromeSinglyLinkedList.Node node3 = new PalindromeSinglyLinkedList.Node(1);
+        node1.next = node2;
+        node2.next = node3;
+        assertTrue(PalindromeSinglyLinkedList.isPalindromeOptimised(node1));
+    }
+
+    @Test
+    public void testOptimisedWithOddLengthPositive2() {
+        PalindromeSinglyLinkedList.Node node1 = new PalindromeSinglyLinkedList.Node(3);
+        PalindromeSinglyLinkedList.Node node2 = new PalindromeSinglyLinkedList.Node(2);
+        PalindromeSinglyLinkedList.Node node3 = new PalindromeSinglyLinkedList.Node(1);
+        PalindromeSinglyLinkedList.Node node4 = new PalindromeSinglyLinkedList.Node(2);
+        PalindromeSinglyLinkedList.Node node5 = new PalindromeSinglyLinkedList.Node(3);
+        node1.next = node2;
+        node2.next = node3;
+        node3.next = node4;
+        node4.next = node5;
+        assertTrue(PalindromeSinglyLinkedList.isPalindromeOptimised(node1));
+    }
+
+    @Test
+    public void testOptimisedWithEvenLengthPositive() {
+        PalindromeSinglyLinkedList.Node node1 = new PalindromeSinglyLinkedList.Node(10);
+        PalindromeSinglyLinkedList.Node node2 = new PalindromeSinglyLinkedList.Node(20);
+        PalindromeSinglyLinkedList.Node node3 = new PalindromeSinglyLinkedList.Node(20);
+        PalindromeSinglyLinkedList.Node node4 = new PalindromeSinglyLinkedList.Node(10);
+        node1.next = node2;
+        node2.next = node3;
+        node3.next = node4;
+        assertTrue(PalindromeSinglyLinkedList.isPalindromeOptimised(node1));
+    }
+
+    @Test
+    public void testOptimisedWithOddLengthNegative() {
+        PalindromeSinglyLinkedList.Node node1 = new PalindromeSinglyLinkedList.Node(1);
+        PalindromeSinglyLinkedList.Node node2 = new PalindromeSinglyLinkedList.Node(2);
+        PalindromeSinglyLinkedList.Node node3 = new PalindromeSinglyLinkedList.Node(2);
+        node1.next = node2;
+        node2.next = node3;
+        assertFalse(PalindromeSinglyLinkedList.isPalindromeOptimised(node1));
+    }
+
+    @Test
+    public void testOptimisedWithEvenLengthNegative() {
+        PalindromeSinglyLinkedList.Node node1 = new PalindromeSinglyLinkedList.Node(10);
+        PalindromeSinglyLinkedList.Node node2 = new PalindromeSinglyLinkedList.Node(20);
+        PalindromeSinglyLinkedList.Node node3 = new PalindromeSinglyLinkedList.Node(20);
+        PalindromeSinglyLinkedList.Node node4 = new PalindromeSinglyLinkedList.Node(20);
+        node1.next = node2;
+        node2.next = node3;
+        node3.next = node4;
+        assertFalse(PalindromeSinglyLinkedList.isPalindromeOptimised(node1));
+    }
 }