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

docs/hackerrank/warmup/interview_preparation_kit/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 × 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
+```

exercises/hackerrank/interview_preparation_kit/arrays/2d_array.go

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+/**
+ * @link Problem definition [[docs/hackerrank/warmup/interview_preparation_kit/2d_array.md]]
+ */
+
+package hackerrank
+
+func getHourGlass(arr [][]int32, positionX int32, positionY int32) []int32 {
+	result := []int32{}
+
+	// top
+	result = append(result, arr[positionX-1][positionY-1])
+	result = append(result, arr[positionX-1][positionY])
+	result = append(result, arr[positionX-1][positionY+1])
+
+	// middle
+	result = append(result, arr[positionX][positionY])
+
+	// bottom
+	result = append(result, arr[positionX+1][positionY-1])
+	result = append(result, arr[positionX+1][positionY])
+	result = append(result, arr[positionX+1][positionY+1])
+
+	return result
+}
+
+func hourglassSum(arr [][]int32) int32 {
+	// Write your code here
+	matrixSize := len(arr)
+
+	matrixStartIndex := 1
+	matrixEndIndex := matrixSize - 2
+
+	var maxHourglassSum int32 = 0
+
+	for i := int32(matrixStartIndex); i <= int32(matrixEndIndex); i++ {
+		for j := int32(matrixStartIndex); j <= int32(matrixEndIndex); j++ {
+			var currentHourglassSum int32 = 0
+			currentHourglass := getHourGlass(arr, i, j)
+			for k := 0; k < len(currentHourglass); k++ {
+				currentHourglassSum += currentHourglass[k]
+			}
+
+			if currentHourglassSum > maxHourglassSum {
+				maxHourglassSum = currentHourglassSum
+			}
+		}
+	}
+
+	return maxHourglassSum
+}

exercises/hackerrank/interview_preparation_kit/arrays/2d_array.testcases.json

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+[
+  {
+    "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
+  }
+]

exercises/hackerrank/interview_preparation_kit/arrays/2d_array_test.go

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+package hackerrank
+
+import (
+	"fmt"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"gon.cl/algorithms/utils"
+)
+
+type TestCase struct {
+	Input    [][]int32 `json:"input"`
+	Expected int32     `json:"expected"`
+}
+
+var testCases []TestCase
+
+// You can use testing.T, if you want to test the code without benchmarking
+func setupSuite(t testing.TB) {
+	wd, _ := os.Getwd()
+	filepath := wd + "/2d_array.testcases.json"
+	t.Log("Setup test cases from JSON: ", filepath)
+
+	var _, err = utils.LoadJSON(filepath, &testCases)
+	if err != nil {
+		t.Log(err)
+	}
+}
+
+func Test2DArray(t *testing.T) {
+
+	setupSuite(t)
+
+	for _, tt := range testCases {
+		testname := fmt.Sprintf("hourglassSum(%v) => %v \n", tt.Input, tt.Expected)
+		t.Run(testname, func(t *testing.T) {
+
+			ans := hourglassSum(tt.Input)
+			assert.Equal(t, tt.Expected, ans)
+		})
+
+	}
+}