[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` `#arrays`
+
+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/lib/exercises/include/exercises/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.hpp

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+#pragma once
+
+#include <vector>
+
+using std::vector;
+
+namespace hackerrank::interview_preparation_kit::arrays {
+
+vector<int> rotLeft(vector<int> a, int d);
+
+} // namespace hackerrank::interview_preparation_kit::arrays

src/lib/exercises/src/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.cpp

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+#include <stdlib.h>
+
+#include <exercises/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.hpp>
+
+/**
+ * @link Problem definition
+ * [[docs/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.md]]
+ */
+
+namespace hackerrank::interview_preparation_kit::arrays {
+
+// cppcheck-suppress passedByValue
+vector<int> rotLeft(vector<int> a, int d) {
+  size_t a_count = a.size();
+  std::vector result(a_count, 0);
+
+  int rotations = d % a.size();
+
+  for (int i = 0; i < a_count; ++i) {
+    size_t new_position = (i + a_count - rotations) % a_count;
+    result[new_position] = a[i];
+  }
+
+  return result;
+}
+
+} // namespace hackerrank::interview_preparation_kit::arrays

src/tests/unit/lib/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.test.cpp

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+// 3rd party libs
+#include <catch2/catch_test_macros.hpp>
+#include <nlohmann/json.hpp>
+
+// local libs
+#include <exercises/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.hpp>
+
+// std libs
+#include <filesystem>
+#include <fstream>
+#include <vector>
+
+using json = nlohmann::json;
+
+TEST_CASE("rotLeft JSON Test Cases", "[jsontestcase] [hackerrank] [arrays]") {
+  SECTION("rotLeft: Normal workflow") {
+    std::filesystem::path path = std::filesystem::path(__FILE__).parent_path() /
+                                 "ctci_array_left_rotation.testcases.json";
+
+    INFO("rotLeft JSON test cases FILE: " << path.string());
+
+    std::ifstream f(path);
+    json data = json::parse(f);
+
+    for (const auto &testcase : data) {
+      const vector<int> result =
+          hackerrank::interview_preparation_kit::arrays::rotLeft(
+              testcase["input"], testcase["d_rotations"]);
+      CHECK(result == testcase["expected"]);
+    }
+  }
+}

src/tests/unit/lib/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.testcases.json

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+[
+  {
+    "title": "Own 0",
+    "input": [1, 2, 3, 4, 5],
+    "d_rotations": 1,
+    "expected": [2, 3, 4, 5, 1]
+  },
+  {
+    "title": "Own 1",
+    "input": [2, 3, 4, 5, 1],
+    "d_rotations": 1,
+    "expected": [3, 4, 5, 1, 2]
+  },
+  {
+    "title": "Own 2",
+    "input": [3, 4, 5, 1, 2],
+    "d_rotations": 1,
+    "expected": [4, 5, 1, 2, 3]
+  },
+  {
+    "title": "Own 3",
+    "input": [4, 5, 1, 2, 3],
+    "d_rotations": 1,
+    "expected": [5, 1, 2, 3, 4]
+  },
+  {
+    "title": "Own 4",
+    "input": [5, 1, 2, 3, 4],
+    "d_rotations": 1,
+    "expected": [1, 2, 3, 4, 5]
+  },
+  {
+    "title": "Sample Test case 0",
+    "input": [1, 2, 3, 4, 5],
+    "d_rotations": 4,
+    "expected": [5, 1, 2, 3, 4]
+  },
+  {
+    "title": "Sample Test case 1",
+    "input": [
+      41, 73, 89, 7, 10, 1, 59, 58, 84, 77, 77, 97, 58, 1, 86, 58, 26, 10, 86,
+      51
+    ],
+    "d_rotations": 10,
+    "expected": [
+      77, 97, 58, 1, 86, 58, 26, 10, 86, 51, 41, 73, 89, 7, 10, 1, 59, 58, 84,
+      77
+    ]
+  },
+  {
+    "title": "Sample Test case 2",
+    "input": [33, 47, 70, 37, 8, 53, 13, 93, 71, 72, 51, 100, 60, 87, 97],
+    "d_rotations": 13,
+    "expected": [87, 97, 33, 47, 70, 37, 8, 53, 13, 93, 71, 72, 51, 100, 60]
+  }
+]