[Hacker Rank] Interview Preparation Kit: Arrays: Array Manipulation. Solved ✅.

[Hacker Rank] Interview Preparation Kit: Arrays: Array Manipulation. Unit Test started.

Author: Gonzalo Diaz

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

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+package ae.hackerrank.interview_preparation_kit.arrays;
+
+import java.util.Arrays;
+import java.util.List;
+
+
+/**
+ * Arrays Left Rotation.
+ *
+ * @link Problem definition [[docs/hackerrank/interview_preparation_kit/arrays/ctci_array_left_rotation.md]]
+ */
+public class CrushOptimized {
+
+  private CrushOptimized() {
+  }
+
+  static java.util.logging.Logger logger = util.CustomLogger.getLogger();
+
+  /**
+   * arrayManipulation.
+   */
+  public static long arrayManipulation(int n, List<List<Integer>> queries) {
+    // why adding 2?
+    //   first slot to adjust 1-based index and
+    //   last slot for storing accum_sum result
+    int[] result = new int[n + 2];
+    Arrays.fill(result, 0);
+    int maximum = 0;
+
+    for (List<Integer> query : queries) {
+      int a = query.get(0);
+      int b = query.get(1);
+      int k = query.get(2);
+
+      // Prefix
+      result[a] += k;
+      result[b + 1] -= k;
+
+      int accumSum = 0;
+      for (int value : result) {
+        accumSum += value;
+        maximum = Math.max(maximum, accumSum);
+      }
+    }
+
+    return maximum;
+  }
+}

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

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+package ae.hackerrank.interview_preparation_kit.arrays;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import java.io.File;
+import java.io.IOException;
+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 CrushTest {
+
+  public static class CrushTestCase {
+    public String title;
+    public Integer n;
+    public List<List<Integer>> queries;
+    public long expected;
+  }
+
+  List<CrushTestCase> testCases;
+
+  @BeforeAll
+  public void setup() throws IOException {
+    ObjectMapper objectMapper = new ObjectMapper();
+
+    String path = String.join("/", "hackerrank",
+        "interview_preparation_kit",
+        "arrays",
+        "crush.testcases.json");
+    File file = new File(
+        this.getClass()
+        .getClassLoader()
+        .getResource(path)
+        .getFile()
+    );
+
+    ObjectMapper mapper = new ObjectMapper();
+    this.testCases  = mapper.readerForListOf(CrushTestCase.class)
+        .readValue(objectMapper.readTree(file));
+  }
+
+  @Test void testArrayManipulation() {
+    for (CrushTestCase testCase : testCases) {
+      long solutionFound = CrushOptimized
+          .arrayManipulation(testCase.n, testCase.queries);
+
+      assertEquals(testCase.expected, solutionFound,
+          String.format("%s(%d, %s) answer must be: %s",
+            "CrushOptimized.arrayManipulation",
+            testCase.n,
+            testCase.queries.toString(),
+            testCase.expected
+          )
+      );
+    }
+  }
+}

algorithm-exercises-java/src/test/resources/hackerrank/interview_preparation_kit/arrays/crush.testcases.json

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+[
+    {
+        "title": "Sample Test Case 0",
+        "n": 5,
+        "queries": [[1, 2, 100],
+                    [2, 5, 100],
+                    [3, 4, 100]],
+        "expected": 200
+    },
+    {
+        "title": "Sample Test Case 1",
+        "n": 10,
+        "queries": [[1, 5, 3],
+                    [4, 8, 7],
+                    [6, 9, 1]],
+        "expected": 10
+    },
+    {
+        "title": "Sample Test Case 3",
+        "n": 10,
+        "queries": [[2, 6, 8],
+                    [3, 5, 7],
+                    [1, 8, 1],
+                    [5, 9, 15]],
+        "expected": 31
+    }
+]