[Hacker Rank] Interview Preparation Kit: Arrays: Left Rotation. Solve…

docs/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.md

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+# [Arrays: Left Rotation](https://www.hackerrank.com/challenges/ctci-array-left-rotation)
+
+Given an array and a number, d, perform d left rotations on the array.
+
+- Difficulty: #easy
+- Category: #ProblemSolvingBasic
+
+A left rotation operation on an array shifts each of the array's elements
+$ 1 $ unit to the left. For example, if $ 2 $ left rotations are performed
+on array $ [1, 2, 3, 4, 5] $, then the array would become $ [3, 4, 5, 1, 2] $.
+Note that the lowest index item moves to the highest index in a rotation.
+This is called a circular array.
+
+Given an array $ a $ of $ n $ integers and a number, $ d $, perform $ d $ left
+rotations on the array. Return the updated array to be printed as a single
+line of space-separated integers.
+
+## Function Description
+
+Complete the function rotLeft in the editor below.
+
+rotLeft has the following parameter(s):
+
+- int a[n]: the array to rotate
+- int d: the number of rotations
+
+## Returns
+
+- int a'[n]: the rotated array
+
+## Input Format
+
+The first line contains two space-separated integers $ n $ and $ d $, the size
+of $ a $ and the number of left rotations.
+The second line contains $ n $ space-separated integers, each an $ a[i] $.
+
+## Constraints
+
+- $ 1 \leq n \leq 10^5 $
+- $ 1 \leq d \leq n $
+- $ 1 \leq a[i] \leq 10^6 $
+
+## Sample Input
+
+```text
+5 4
+1 2 3 4 5
+```
+
+## Sample Output
+
+```text
+5 1 2 3 4
+```
+
+## Explanation
+
+When we perform $ d = 4 $ left rotations, the array undergoes the following
+sequence of changes:
+
+> [1, 2, 3, 4, 5]
+> -> [2, 3, 4, 5, 1]
+> -> [3, 4, 5, 1, 2]
+> -> [4, 5, 1, 2, 3]
+> -> [5, 1, 2, 3, 4]

src/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.js

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+/**
+ * @link Problem definition [[docs/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.md]]
+ */
+
+export function rotLeftOne(aNumbers) {
+  const first = aNumbers.shift();
+  if (first !== undefined) {
+    aNumbers.push(first);
+  }
+
+  return aNumbers;
+}
+
+export function rotLeft(aNumbers, dRotations) {
+  let output = [...aNumbers];
+
+  for (let i = 0; i < dRotations; i++) {
+    output = rotLeftOne(output);
+  }
+
+  return output;
+}
+
+export default { rotLeft, rotLeftOne };

src/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.test.js

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+import { describe, expect, it } from '@jest/globals';
+import { logger as console } from '../../../logger.js';
+
+import { rotLeft, rotLeftOne } from './ctci_array_left_rotation.js';
+
+const ROT_LEFT_ONE_TEST_CASES = [
+  { numbers: [1, 2, 3, 4, 5], expected: [2, 3, 4, 5, 1] },
+  { numbers: [2, 3, 4, 5, 1], expected: [3, 4, 5, 1, 2] },
+  { numbers: [3, 4, 5, 1, 2], expected: [4, 5, 1, 2, 3] },
+  { numbers: [4, 5, 1, 2, 3], expected: [5, 1, 2, 3, 4] },
+  { numbers: [5, 1, 2, 3, 4], expected: [1, 2, 3, 4, 5] }
+];
+
+const ROT_LEFT_TEST_CASES = [
+  { numbers: [1, 2, 3, 4, 5], d_rotations: 4, expected: [5, 1, 2, 3, 4] }
+];
+
+describe('ctci_array_left_rotation', () => {
+  it('rotLeftOne Test Cases', () => {
+    expect.assertions(5);
+
+    ROT_LEFT_ONE_TEST_CASES.forEach((value) => {
+      const answer = rotLeftOne(value.numbers);
+
+      console.debug(`rotLeftOne(${value.numbers}) solution found: ${answer}`);
+
+      expect(answer).toStrictEqual(value.expected);
+    });
+  });
+
+  it('rotLeft Test cases', () => {
+    expect.assertions(1);
+
+    ROT_LEFT_TEST_CASES.forEach((value) => {
+      const answer = rotLeft(value.numbers, value.d_rotations);
+
+      console.debug(`rotLeft(${value.numbers}) solution found: ${answer}`);
+
+      expect(answer).toStrictEqual(value.expected);
+    });
+  });
+});