[Hacker Rank] Interview Preparation Kit: Array: 2D Array - DS. Solved ✅.

Author: Gonzalo Diaz

algorithm-exercises-java/src/main/java/ae/hackerrank/interview_preparation_kit/arrays/TwoDarray.java

@@ -16,10 +16,6 @@ private TwoDarray() { }
   private static List<Integer> getHourGlass(List<List<Integer>> arr, int positionX, int positionY) {
     List<Integer> result = new ArrayList<>();
 
-    if (arr  == null || arr.isEmpty()) {
-      return result;
-    }
-
     // top
     result.add(arr.get(positionX - 1).get(positionY - 1));
     result.add(arr.get(positionX - 1).get(positionY));

algorithm-exercises-java/src/test/java/ae/hackerrank/interview_preparation_kit/arrays/TwoDarrayTest.java

@@ -3,6 +3,7 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.List;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
@@ -33,18 +34,43 @@ public void setup() throws IOException {
   }
 
 
-  @Test void testArrayManipulation() {
+  @Test void testHourglassSum() {
     for (TwoDarrayTestCase testCase : testCases) {
       long solutionFound = TwoDarray.hourglassSum(testCase.input);
 
       assertEquals(testCase.expected, solutionFound,
           "%s(%s) answer must be: %s".formatted(
-            "CrushOptimized.arrayManipulation",
+            "TwoDarray.hourglassSum",
             testCase.input.toString(),
             testCase.expected
             )
       );
     }
   }
+
+  @Test void testHourglassSumEdgeCases() {
+    List<List<Integer>> input = null;
+    Integer expected = null;
+    Integer solutionFound = TwoDarray.hourglassSum(null);
+    assertEquals(expected, solutionFound,
+        "%s(%s) answer must be: %s".formatted(
+          "TwoDarray.hourglassSum",
+          input,
+          expected
+          )
+    );
+
+    input = new ArrayList<List<Integer>>();
+    expected = null;
+    solutionFound = TwoDarray.hourglassSum(null);
+
+    assertEquals(expected, solutionFound,
+        "%s(%s) answer must be: %s".formatted(
+          "TwoDarray.hourglassSum",
+          input,
+          expected
+          )
+    );
+  }
 }