[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

@@ -16,6 +16,10 @@ 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));
@@ -38,10 +42,12 @@ private static List<Integer> getHourGlass(List<List<Integer>> arr, int positionX
   public static Integer hourglassSum(List<List<Integer>> arr) {
     int matrixSize = 0;
 
-    if (arr != null) {
-      matrixSize = arr.size();
+    if (arr == null) {
+      return null;
     }
 
+    matrixSize = arr.size();
+
     int matrixStartIndex = 1;
     int matrixEndIndex = matrixSize - 2;