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

Author: Gonzalo Diaz

src/hackerrank/interview_preparation_kit/arrays/2d_array.test.ts

@@ -0,0 +1,21 @@
+import { describe, expect, it } from '@jest/globals';
+import { logger as console } from '../../../logger';
+
+import { hourglassSum } from './2d_array';
+import TEST_CASES from './2d_array.testcases_test.json';
+
+describe('arrays: 2d Array hourglassSum', () => {
+  it('hourglassSum Test Cases', () => {
+    expect.assertions(1);
+
+    TEST_CASES.forEach((test) => {
+      const answer = hourglassSum(test.input);
+
+      console.debug(
+        `gethourGlass(${test.input.toString()}) solution found: ${answer}`
+      );
+
+      expect(answer).toStrictEqual(test.expected);
+    });
+  });
+});

src/hackerrank/interview_preparation_kit/arrays/2d_array.testcases_test.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
+  }
+]

src/hackerrank/interview_preparation_kit/arrays/2d_array.ts

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+export function gethourGlass(
+  arr: number[][],
+  positionX: number,
+  positionY: number
+): number[] {
+  const result: number[] = [];
+
+  // top
+  result.push(arr[positionX - 1][positionY - 1]);
+  result.push(arr[positionX - 1][positionY]);
+  result.push(arr[positionX - 1][positionY + 1]);
+  // middle
+  result.push(arr[positionX][positionY]);
+  // bottom
+  result.push(arr[positionX + 1][positionY - 1]);
+  result.push(arr[positionX + 1][positionY]);
+  result.push(arr[positionX + 1][positionY + 1]);
+  return result;
+}
+
+export function hourglassSum(arr: number[][]): number | null {
+  let matrixSize = 0;
+
+  if (arr?.[0]) {
+    matrixSize = arr.length;
+  }
+
+  const matrixStartIndex = 1;
+  const matrixStopIndex = matrixSize - 2;
+
+  console.debug(`matrix size ${matrixSize}`);
+
+  let maxHourglassSum: number | null = null;
+
+  // recorrido
+  for (let i = matrixStartIndex; i <= matrixStopIndex; i++) {
+    for (let j = matrixStartIndex; j <= matrixStopIndex; j++) {
+      // hourglass centers
+      console.debug(`posicion (${i},${j}): ${arr[i][j]}`);
+
+      const houglassValues: number[] = gethourGlass(arr, i, j);
+
+      const thisHourglassSum = houglassValues.reduce(
+        (a: number, b: number): number => a + b,
+        0
+      );
+
+      console.debug(houglassValues, `thisHourglassSum: ${thisHourglassSum}`);
+
+      if (
+        maxHourglassSum === undefined ||
+        maxHourglassSum === null ||
+        thisHourglassSum > maxHourglassSum
+      ) {
+        maxHourglassSum = thisHourglassSum;
+      }
+    }
+  }
+
+  return maxHourglassSum;
+}
+
+export default { hourglassSum };