Merge pull request #178 from sir-gon/feature/array-left-rotation

Feature/array left rotation

Author: sir-gon

algorithm-exercises-java/src/main/java/ae/hackerrank/interview_preparation_kit/arrays/ArraysLeftRotation.java

@@ -0,0 +1,50 @@
+package ae.hackerrank.interview_preparation_kit.arrays;
+
+import java.util.ArrayList;
+import java.util.List;
+
+
+/**
+ * Arrays Left Rotation.
+ *
+ * @link Problem definition [[docs/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.md]]
+ */
+public class ArraysLeftRotation {
+
+  private ArraysLeftRotation() {
+  }
+
+  static java.util.logging.Logger logger = util.CustomLogger.getLogger();
+  static final int FIRST_POSITION = 0;
+
+  /**
+   * rotLeftOne.
+   */
+  public static List<Integer> rotLeftOne(List<Integer> a) {
+    // Clone the list
+    List<Integer> output = new ArrayList<>(a);
+
+    Integer first = output.get(FIRST_POSITION);
+    output.remove(FIRST_POSITION);
+    output.add(first);
+
+    return output;
+  }
+
+  /**
+   * rotLeft.
+   */
+  public static List<Integer> rotLeft(List<Integer> a, int d) {
+
+    // Clone the list
+    List<Integer> output = new ArrayList<>(a);
+
+    int i = 1;
+    while (i <= d) {
+      output = rotLeftOne(output);
+      i += 1;
+    }
+
+    return output;
+  }
+}

algorithm-exercises-java/src/test/java/ae/hackerrank/interview_preparation_kit/arrays/ArraysLeftRotationTest.java

@@ -0,0 +1,86 @@
+package ae.hackerrank.interview_preparation_kit.arrays;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Arrays;
+import java.util.List;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+import org.junit.jupiter.api.TestInstance.Lifecycle;
+
+
+@TestInstance(Lifecycle.PER_CLASS)
+  class ArraysLeftRotationTest {
+
+  public class ArraysLeftRotationTestCase {
+    public List<Integer> input;
+    public List<Integer> expected;
+
+    public ArraysLeftRotationTestCase(List<Integer> input, List<Integer> expected) {
+      this.input = input;
+      this.expected = expected;
+    }
+  }
+
+  public class ArraysLeftRotationsTestCase {
+    public List<Integer> input;
+    public Integer d;
+    public List<Integer> expected;
+
+    public ArraysLeftRotationsTestCase(List<Integer> input, Integer d, List<Integer> expected) {
+      this.input = input;
+      this.d = d;
+      this.expected = expected;
+    }
+  }
+
+  public List<ArraysLeftRotationTestCase> testCases;
+  public List<ArraysLeftRotationsTestCase> testRotationsCases;
+
+  @BeforeAll
+  public void setup() {
+    this.testCases = Arrays.asList(
+      new ArraysLeftRotationTestCase(Arrays.asList(1, 2, 3, 4, 5), Arrays.asList(2, 3, 4, 5, 1)),
+      new ArraysLeftRotationTestCase(Arrays.asList(2, 3, 4, 5, 1), Arrays.asList(3, 4, 5, 1, 2)),
+      new ArraysLeftRotationTestCase(Arrays.asList(3, 4, 5, 1, 2), Arrays.asList(4, 5, 1, 2, 3)),
+      new ArraysLeftRotationTestCase(Arrays.asList(4, 5, 1, 2, 3), Arrays.asList(5, 1, 2, 3, 4)),
+      new ArraysLeftRotationTestCase(Arrays.asList(5, 1, 2, 3, 4), Arrays.asList(1, 2, 3, 4, 5))
+    );
+
+    this.testRotationsCases = Arrays.asList(
+      new ArraysLeftRotationsTestCase(
+        Arrays.asList(1, 2, 3, 4, 5),
+        4,
+        Arrays.asList(5, 1, 2, 3, 4))
+    );
+  }
+
+  @Test void testRotLeftOne() {
+    for (ArraysLeftRotationTestCase testCase : this.testCases) {
+      List<Integer> solutionFound = ArraysLeftRotation.rotLeftOne(testCase.input);
+
+      assertEquals(testCase.expected, solutionFound,
+          String.format("%s(%s) answer must be: %s",
+            "CompareTriplets.compareTriplets",
+            testCase.input.toString(),
+            testCase.expected.toString())
+      );
+    }
+  }
+
+  @Test void testRotLeft() {
+    for (ArraysLeftRotationsTestCase testCase : this.testRotationsCases) {
+      List<Integer> solutionFound = ArraysLeftRotation.rotLeft(testCase.input, testCase.d);
+
+      assertEquals(testCase.expected, solutionFound,
+          String.format("%s(%s, %d) answer must be: %s",
+            "CompareTriplets.compareTriplets",
+            testCase.input.toString(),
+            testCase.d,
+            testCase.expected.toString())
+      );
+    }
+  }
+
+}

config/checkstyle/checkstyle.xml

@@ -45,7 +45,7 @@
   <module name="LineLength">
     <property name="fileExtensions" value="java"/>
     <property name="max" value="100"/>
-    <property name="ignorePattern" value="^package.*|^import.*|a href|href|http://|https://|ftp://"/>
+    <property name="ignorePattern" value="^package.*|^import.*|a href|href|http://|https://|ftp://|[[*]]"/>
   </module>
 
   <module name="TreeWalker">
@@ -185,7 +185,7 @@
              value="Type name ''{0}'' must match pattern ''{1}''."/>
     </module>
     <module name="MemberName">
-      <property name="format" value="^[_]*[a-z][a-z0-9][a-zA-Z0-9]*$"/>
+      <property name="format" value="^[_]*[a-z][a-zA-Z0-9]*$"/>
       <message key="name.invalidPattern"
              value="Member name ''{0}'' must match pattern ''{1}''."/>
     </module>

docs/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.md

@@ -0,0 +1,65 @@
+# [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]