Merge pull request #169 from sir-gon/feature/2d_array

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

Author: sir-gon

algorithm_exercises_csharp/src/hackerrank/interview_preparation_kit/arrays/TwoDArray.cs

@@ -0,0 +1,65 @@
+namespace algorithm_exercises_csharp.hackerrank.interview_preparation_kit;
+
+using System.Diagnostics.CodeAnalysis;
+
+/**
+  * 2D Array - DS.
+  *
+  * @link Problem definition [[docs/hackerrank/interview_preparation_kit/arrays/2d_array.md]]
+  */
+
+public class TwoDArray
+{
+  [ExcludeFromCodeCoverage]
+  protected TwoDArray() { }
+
+  private static List<int> getHourGlass(List<List<int>> arr, int positionX, int positionY)
+  {
+    List<int> result = [];
+
+    // top
+    result.Add(arr[positionX - 1][positionY - 1]);
+    result.Add(arr[positionX - 1][positionY]);
+    result.Add(arr[positionX - 1][positionY + 1]);
+
+    // middle
+    result.Add(arr[positionX][positionY]);
+
+    // bottom
+    result.Add(arr[positionX + 1][positionY - 1]);
+    result.Add(arr[positionX + 1][positionY]);
+    result.Add(arr[positionX + 1][positionY + 1]);
+
+    return result;
+  }
+
+  public static int hourglassSum(List<List<int>> arr)
+  {
+    int matrixSize = 0;
+
+    if (arr.Count > 0)
+    {
+      matrixSize = arr.Count;
+    }
+
+    int matrixStartIndex = 1;
+    int matrixEndIndex = matrixSize - 2;
+
+    int? maxHourGlassSum = null;
+
+    for (int i = matrixStartIndex; i <= matrixEndIndex; i++)
+    {
+      for (int j = matrixStartIndex; j <= matrixEndIndex; j++)
+      {
+        int hourGlassSum = getHourGlass(arr, i, j).Sum();
+
+        if (maxHourGlassSum == null || hourGlassSum > maxHourGlassSum)
+        {
+          maxHourGlassSum = hourGlassSum;
+        }
+      }
+    }
+
+    return maxHourGlassSum ?? 0;
+  }
+}

algorithm_exercises_csharp_test/Resources/hackerrank/interview_preparation_kit/arrays/2d_array.testcases.json

@@ -0,0 +1,14 @@
+[
+  {
+    "title": "Sample Test Case 0",
+    "input": [
+      [1, 1, 1, 0, 0, 0],
+      [0, 1, 0, 0, 0, 0],
+      [1, 1, 1, 0, 0, 0],
+      [0, 0, 2, 4, 4, 0],
+      [0, 0, 0, 2, 0, 0],
+      [0, 0, 1, 2, 4, 0]
+    ],
+    "expected": 19
+  }
+]

algorithm_exercises_csharp_test/src/hackerrank/interview_preparation_kit/arrays/TwoDArray.Test.cs

@@ -0,0 +1,35 @@
+namespace algorithm_exercises_csharp.hackerrank.interview_preparation_kit;
+
+[TestClass]
+public class TwoDArrayTest
+{
+  public class TwoDArrayTestCase
+  {
+    public string title { get; set; } = default!;
+    public List<List<int>> input { get; set; } = default!;
+    public long expected { get; set; } = default!;
+  }
+
+  private List<TwoDArrayTestCase> testCases { get; set; } = default!;
+
+  [TestInitialize]
+  public void testInitialize()
+  {
+    testCases = JsonLoader.resourceLoad<List<TwoDArrayTestCase>>(
+      "hackerrank/interview_preparation_kit/arrays/2d_array.testcases.json"
+    ) ?? [];
+  }
+
+  [TestMethod]
+  public void testHourglassSum()
+  {
+    long result;
+
+    foreach (TwoDArrayTestCase test in testCases)
+    {
+      result = TwoDArray.hourglassSum(test.input);
+      Assert.AreEqual(test.expected, result);
+    }
+  }
+}
+

docs/hackerrank/interview_preparation_kit/arrays/2d_array.md

@@ -0,0 +1,135 @@
+# [Arrays: 2D Array - DS](https://www.hackerrank.com/challenges/2d-array)
+
+- Difficulty:  ` #easy `
+- Category: ` #ProblemSolvingBasic `
+
+Given a 6 × 6  2D Array, `arr`:
+
+```text
+1 1 1 0 0 0
+0 1 0 0 0 0
+1 1 1 0 0 0
+0 0 0 0 0 0
+0 0 0 0 0 0
+0 0 0 0 0 0
+```
+
+An hourglass in `A` is a subset of values with indices falling in this pattern
+ in `arr`'s graphical representation:
+
+```text
+a b c
+  d
+e f g
+```
+
+There are `16` hourglasses in `arr`.
+An hourglass sum is the sum of an hourglass' values.
+Calculate the hourglass sum for every hourglass in `arr`,
+then print the maximum hourglass sum. The array will always be 6 × 6.
+
+## Example
+
+arr =
+
+```text
+-9 -9 -9  1 1 1
+ 0 -9  0  4 3 2
+-9 -9 -9  1 2 3
+ 0  0  8  6 6 0
+ 0  0  0 -2 0 0
+ 0  0  1  2 4 0
+```
+
+The `16` hourglass sums are:
+
+```text
+-63, -34, -9, 12,
+-10,   0, 28, 23,
+-27, -11, -2, 10,
+  9,  17, 25, 18
+```
+
+The highest hourglass sum is `26` from the hourglass beginning
+at row `1`, column `2`:
+
+```text
+0 4 3
+  1
+8 6 6
+````
+
+**Note**: If you have already solved the Java domain's Java 2D Array challenge,
+you may wish to skip this challenge.
+
+## Function Description
+
+Complete the function hourglassSum in the editor below.
+
+hourglassSum has the following parameter(s):
+
+- `int arr[6][6]`: an array of integers
+
+## Returns
+
+- int: the maximum hourglass sum
+
+## Input Format
+
+Each of the `6` lines of inputs `arr[i]` contains space-separated integers `arr[i][j]`.
+
+## Constraints
+
+- $9 \leq arr[i][j] \leq 9$
+- $0 \leq i, j \leq 5$
+
+## Output Format
+
+Print the largest (maximum) hourglass sum found in `arr`.
+
+## Sample Input
+
+```text
+1 1 1 0 0 0
+0 1 0 0 0 0
+1 1 1 0 0 0
+0 0 2 4 4 0
+0 0 0 2 0 0
+0 0 1 2 4 0
+```
+
+## Sample Output
+
+```text
+19
+```
+
+## Explanation
+
+`arr` contains the following hourglasses:
+
+```text
+111 110 100 000
+ 1   0   0   0
+111 110 100 000
+
+010 100 000 000
+ 0   1   0   0
+002 024 244 440
+
+111 110 100 000
+ 0   2   4   4
+000 002 020 200
+
+002 024 244 440
+ 0   0   2   0
+001 012 124 240
+```
+
+The hourglass with the maximum sum (`19`) is:
+
+```text
+2 4 4
+  2
+1 2 4
+```