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[Hacker Rank] Interview Preparation Kit: Array: 2D Array - DS. Solved ✅. #169

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sir-gon merged 1 commit into main from feature/2d_array
Jan 22, 2025
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View file Open in desktop
Original file line number Diff line number Diff line change
@@ -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;
}
}
Original file line number Diff line number Diff line change
@@ -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
}
]
Original file line number Diff line number Diff line change
@@ -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);
}
}
}

135 changes: 135 additions & 0 deletions docs/hackerrank/interview_preparation_kit/arrays/2d_array.md
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# [Arrays: 2D Array - DS](https://www.hackerrank.com/challenges/2d-array)

- Difficulty: ` #easy `
- Category: ` #ProblemSolvingBasic `

Given a 6 ×ばつ 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 ×ばつ 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ドル \leq arr[i][j] \leq 9$
- 0ドル \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
```

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