Create NearestElementTest.java

Author: sravyapalla

src/test/java/com/thealgorithms/datastructures/stacks/NearestElementTest.java

@@ -0,0 +1,51 @@
+package datastructures.stacks;
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import org.junit.jupiter.api.Test;
+class NearestElementTest {
+    @Test
+    void testNearestGreaterToRight_basic() {
+        int[] arr = {4, 5, 2, 25};
+        int[] expected = {5, 25, 25, -1};
+        assertArrayEquals(expected, NearestElement.nearestGreaterToRight(arr));
+    }
+    @Test
+    void testNearestGreaterToLeft_basic() {
+        int[] arr = {4, 5, 2, 25};
+        int[] expected = {-1, -1, 5, -1};
+        assertArrayEquals(expected, NearestElement.nearestGreaterToLeft(arr));
+    }
+    @Test
+    void testNearestSmallerToRight_basic() {
+        int[] arr = {4, 5, 2, 25};
+        int[] expected = {2, 2, -1, -1};
+        assertArrayEquals(expected, NearestElement.nearestSmallerToRight(arr));
+    }
+    @Test
+    void testNearestSmallerToLeft_basic() {
+        int[] arr = {4, 5, 2, 25};
+        int[] expected = {-1, 4, -1, 2};
+        assertArrayEquals(expected, NearestElement.nearestSmallerToLeft(arr));
+    }
+    @Test
+    void testEdgeCases_emptyAndSingle() {
+        int[] empty = {};
+        int[] single = {10};
+        assertArrayEquals(new int[]{}, NearestElement.nearestGreaterToRight(empty));
+        assertArrayEquals(new int[]{-1}, NearestElement.nearestGreaterToRight(single));
+        assertArrayEquals(new int[]{-1}, NearestElement.nearestGreaterToLeft(single));
+        assertArrayEquals(new int[]{-1}, NearestElement.nearestSmallerToRight(single));
+        assertArrayEquals(new int[]{-1}, NearestElement.nearestSmallerToLeft(single));
+    }
+    @Test
+    void testDuplicates() {
+        int[] arr = {2, 2, 2};
+        int[] ngr = {-1, -1, -1}; // strictly greater required
+        int[] ngl = {-1, -1, -1};
+        int[] nsr = {-1, -1, -1}; // strictly smaller required
+        int[] nsl = {-1, -1, -1};
+        assertArrayEquals(ngr, NearestElement.nearestGreaterToRight(arr));
+        assertArrayEquals(ngl, NearestElement.nearestGreaterToLeft(arr));
+        assertArrayEquals(nsr, NearestElement.nearestSmallerToRight(arr));
+        assertArrayEquals(nsl, NearestElement.nearestSmallerToLeft(arr));
+    }
+}