[Hacker Rank] Interview Preparation Kit: Dictionaries and Hashmaps: C…

src/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/count_triplets_1_bruteforce.js

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+/**
+ * @link Problem definition [[docs/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/count_triplets_1.md]]
+ * @see Solution Notes: [[docs/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/count_triplets_1-solution-notes.md]]
+ */
+import { logger as console } from '../../../logger.js';
+
+export function countTriplets(arr, ratio) {
+  const size = arr.length;
+  let counter = 0;
+
+  for (let i = 0; i < size - 2; i++) {
+    for (let j = i + 1; j < size - 1; j++) {
+      for (let k = j + 1; k < size; k++) {
+        console.debug(`${arr[i]}, ${arr[j]}, ${arr[k]}`);
+
+        if (ratio * arr[i] === arr[j] && ratio * arr[j] === arr[k]) {
+          counter += 1;
+        }
+      }
+    }
+  }
+
+  return counter;
+}
+
+export default { countTriplets };

src/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/count_triplets_1_bruteforce.test.js

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+import { describe, expect, it } from '@jest/globals';
+import { logger as console } from '../../../logger.js';
+
+import { countTriplets } from './count_triplets_1_bruteforce.js';
+
+const SMALL_TEST_CASES = [
+  {
+    title: 'Sample Test Case 0',
+    input: [1, 2, 2, 4],
+    r: 2,
+    expected: 2
+  },
+  {
+    title: 'Sample Test Case 1',
+    input: [1, 3, 9, 9, 27, 81],
+    r: 3,
+    expected: 6
+  },
+  {
+    title: 'Sample Test Case 1 (unsorted)',
+    input: [9, 3, 1, 81, 9, 27],
+    r: 3,
+    expected: 1
+  },
+  {
+    title: 'Sample Test Case 12',
+    input: [1, 5, 5, 25, 125],
+    r: 5,
+    expected: 4
+  }
+];
+
+describe('count_triplets_1', () => {
+  it('countTriplets test cases', () => {
+    expect.assertions(4);
+
+    SMALL_TEST_CASES.forEach((test) => {
+      const answer = countTriplets(test.input, test.r);
+
+      console.debug(
+        `countTriplets(${test.input}, ${test.r}) solution found: ${answer}`
+      );
+
+      expect(answer).toStrictEqual(test.expected);
+    });
+  });
+});

src/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/count_triplets_1_optimized.test.js

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+import { describe, expect, it } from '@jest/globals';
+import { logger as console } from '../../../logger.js';
+
+import { countTriplets } from './count_triplets_1_optmized.js';
+import SMALL_TEST_CASES from './count_triplets_1_testcases.json';
+
+const BIG_TEST_CASES = [
+  {
+    title: 'Sample Test Case 2',
+    input: [
+      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
+    ],
+    r: 1,
+    expected: 161700
+  }
+];
+
+describe('count_triplets_1 (optimized)', () => {
+  it('countTriplets small test cases', () => {
+    expect.assertions(4);
+
+    SMALL_TEST_CASES.forEach((test) => {
+      const answer = countTriplets(test.input, test.r);
+
+      console.debug(
+        `countTriplets(${test.input}, ${test.r}) solution found: ${answer}`
+      );
+
+      expect(answer).toStrictEqual(test.expected);
+    });
+  });
+
+  it('countTriplets big test cases', () => {
+    expect.assertions(1);
+
+    BIG_TEST_CASES.forEach((test) => {
+      const answer = countTriplets(test.input, test.r);
+
+      console.debug(
+        `countTriplets(${test.input}, ${test.r}) solution found: ${answer}`
+      );
+
+      expect(answer).toStrictEqual(test.expected);
+    });
+  });
+});

src/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/count_triplets_1_optmized.js

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+/**
+ * @link Problem definition [[docs/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/count_triplets_1.md]]
+ * @see Solution Notes: [[docs/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/count_triplets_1-solution-notes.md]]
+ */
+
+export function countTriplets(arr, ratio) {
+  let triplets = 0;
+
+  const aCounter = arr.reduce((accumulator, entry) => {
+    if (entry in accumulator) {
+      accumulator[entry] += 1;
+    } else {
+      accumulator[entry] = 1;
+    }
+    return accumulator;
+  }, {});
+
+  const bCounter = {};
+
+  arr.forEach((x) => {
+    const j = Math.floor(x / ratio);
+    const k = x * ratio;
+    aCounter[x] -= 1;
+    if (bCounter[j] && aCounter[k] && x % ratio === 0) {
+      triplets += bCounter[j] * aCounter[k];
+    }
+
+    if (x in bCounter) {
+      bCounter[x] += 1;
+    } else {
+      bCounter[x] = 1;
+    }
+  });
+
+  return triplets;
+}
+
+export default { countTriplets };

src/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/count_triplets_1_testcases.json

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+[
+  {
+    "title": "Sample Test Case 0",
+    "input": [1, 2, 2, 4],
+    "r": 2,
+    "expected": 2
+  },
+  {
+    "title": "Sample Test Case 1",
+    "input": [1, 3, 9, 9, 27, 81],
+    "r": 3,
+    "expected": 6
+  },
+  {
+    "title": "Sample Test Case 1 (unsorted)",
+    "input": [9, 3, 1, 81, 9, 27],
+    "r": 3,
+    "expected": 1
+  },
+  {
+    "title": "Sample Test Case 12",
+    "input": [1, 5, 5, 25, 125],
+    "r": 5,
+    "expected": 4
+  }
+]