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

docs/hackerrank/interview_preparation_kit/arrays/two_d_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
+```

src/hackerrank/interview_preparation_kit/arrays/two_d_array.py

@@ -0,0 +1,45 @@
+# @link Problem definition
+# [[docs/hackerrank/interview_preparation_kit/arrays/two_d_array.md]]
+
+import logging
+
+LOGGER = logging.getLogger(__name__)
+
+
+def gethourglass(arr: list[list[int]], position_x: int, position_y: int) -> list[int]:
+    result: list[int] = []
+
+    # top
+    result.append(arr[position_x - 1][position_y - 1])
+    result.append(arr[position_x - 1][position_y])
+    result.append(arr[position_x - 1][position_y + 1])
+
+    # middle
+    result.append(arr[position_x][position_y])
+
+    # bottom
+    result.append(arr[position_x + 1][position_y - 1])
+    result.append(arr[position_x + 1][position_y])
+    result.append(arr[position_x + 1][position_y + 1])
+
+    return result
+
+
+def hourglass_sum(arr: list[list[int]]) -> int | None:
+    matrix_size: int = len(arr)
+
+    matrix_start_index: int = 1
+    matrix_stop_index: int = matrix_size - 1
+
+    max_hourglass_sum: int | None = None
+
+    for i in range(matrix_start_index, matrix_stop_index):
+        for j in range(matrix_start_index, matrix_stop_index):
+
+            houglass_values: list[int] = gethourglass(arr, i, j)
+            this_hourglass_sum: int = sum(houglass_values)
+
+            if max_hourglass_sum is None or this_hourglass_sum > max_hourglass_sum:
+                max_hourglass_sum = this_hourglass_sum
+
+    return max_hourglass_sum

src/hackerrank/interview_preparation_kit/arrays/two_d_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
+  }
+]

src/hackerrank/interview_preparation_kit/arrays/two_d_array_test.py

@@ -0,0 +1,21 @@
+import unittest
+from pathlib import Path
+
+from ....hackerrank.lib.loader import load_test_cases
+from .two_d_array import hourglass_sum
+
+FILE_PATH = str(Path(__file__).resolve().parent)
+
+TEST_CASES = load_test_cases(
+    FILE_PATH + '/two_d_array.testcases.json')
+
+
+class Test2dArray(unittest.TestCase):
+
+    def test_hourglass_sum(self):
+        for _, _tt in enumerate(TEST_CASES):
+
+            self.assertEqual(
+                hourglass_sum(_tt['input']), _tt['expected'],
+                f"{_} | hourglass_sum({_tt['input']}) must be "
+                f"=> {_tt['expected']}")