Add HackerRank: 2D Array - DS

.gitignore

@@ -24,4 +24,7 @@ hs_err_pid*
 
 # IntelliJ
 **/.idea/*
-*.iml
+*.iml
+
+# Compiled
+target/*

README.md

@@ -21,6 +21,8 @@ HackerRank assigns their problems a difficulty rating (Easy, Medium, Hard, Exper
 
 ### Arrays
 
+- 2D Array - DS (Easy) [Problem](https://www.hackerrank.com/challenges/2d-array/problem) | [Solution](https://github.com/aykrieger/coding-exercises/blob/master/java/src/hackerrank/arrays/TwoDArrayDS.java)
+
 - Minimum Swaps 2 (Medium) [Problem](https://www.hackerrank.com/challenges/minimum-swaps-2/problem) | [Solution](https://github.com/aykrieger/coding-exercises/blob/master/java/src/hackerrank/arrays/MinimumSwaps2.java)
 
 ### Greedy Algorithms

java/src/hackerrank/arrays/TwoDArrayDS.java

@@ -0,0 +1,81 @@
+package hackerrank.arrays;
+
+import static java.util.stream.Collectors.toList;
+
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+
+/**
+ * @see <a href="https://www.hackerrank.com/challenges/2d-array/problem">2D Array - DS</a>
+ */
+public class TwoDArrayDS {
+
+  /*
+   * Complete the 'hourglassSum' function below.
+   *
+   * The function is expected to return an INTEGER.
+   * The function accepts 2D_INTEGER_ARRAY arr as parameter.
+   */
+
+  public static int hourglassSum(List<List<Integer>> arr) {
+    Integer largestSum = null;
+
+    for (int x = 0; x < 4; x++) {
+      for (int y = 0; y < 4; y++) {
+        // Here we begin calculating the sum of a single hourglass
+        int currentSum = 0;
+        for (int i = 0; i < 3; i++) {
+          for (int j = 0; j < 3; j++) {
+            if (i == 1 && (j == 0 || j == 2)) {
+              continue;
+            }
+
+            currentSum = currentSum + arr.get(x + i).get(y + j);
+          }
+        }
+        if (largestSum == null) {
+          largestSum = currentSum;
+        }
+        if (currentSum > largestSum) {
+          largestSum = currentSum;
+        }
+      }
+    }
+    return largestSum;
+  }
+
+  public static void main(String[] args) throws IOException {
+    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
+    BufferedWriter bufferedWriter = new BufferedWriter(
+        new FileWriter(System.getenv("OUTPUT_PATH")));
+
+    List<List<Integer>> arr = new ArrayList<>();
+
+    IntStream.range(0, 6).forEach(i -> {
+      try {
+        arr.add(
+            Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
+                .map(Integer::parseInt)
+                .collect(toList())
+        );
+      } catch (IOException ex) {
+        throw new RuntimeException(ex);
+      }
+    });
+
+    int result = hourglassSum(arr);
+
+    bufferedWriter.write(String.valueOf(result));
+    bufferedWriter.newLine();
+
+    bufferedReader.close();
+    bufferedWriter.close();
+  }
+}