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

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

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+package ae.hackerrank.interview_preparation_kit.arrays;
+
+import java.util.Arrays;
+import java.util.List;
+
+
+/**
+ * Crush (Brute Force).
+ *
+ * @link Problem definition [[docs/hackerrank/interview_preparation_kit/arrays/crush.md]]
+ * @link Solution notes [[docs/hackerrank/interview_preparation_kit/arrays/crush_optimized-solution-notes.md]]
+ */
+public class CrushBruteForce {
+
+  private CrushBruteForce() {
+  }
+
+  static java.util.logging.Logger logger = util.CustomLogger.getLogger();
+
+  private static final int INITIALIZER = 0;
+
+  /**
+   * arrayManipulation.
+   */
+  public static long arrayManipulation(int n, List<List<Integer>> queries) {
+    // why adding 1?
+    //   first slot to adjust 1-based index and
+    int[] result = new int[n + 1];
+    Arrays.fill(result, INITIALIZER);
+    int maximum = INITIALIZER;
+
+    for (List<Integer> query : queries) {
+      int start = query.get(0);
+      int end = query.get(1);
+      int value = query.get(2);
+
+      for (int i = start; i < end + 1; i++) {
+        result[i] += value;
+      }
+
+      for (int current : result) {
+        maximum = Math.max(current, maximum);
+      }
+    }
+
+    return maximum;
+  }
+}

algorithm-exercises-java/src/test/java/ae/hackerrank/interview_preparation_kit/arrays/CrushBruteForceTest.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 CrushBruteForceTest {
+
+  public static class CrushBruteForceTestCase {
+    public String title;
+    public Integer n;
+    public List<List<Integer>> queries;
+    public long expected;
+  }
+
+  List<CrushBruteForceTestCase> 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(CrushBruteForceTestCase.class)
+        .readValue(objectMapper.readTree(file));
+  }
+
+  @Test void testArrayManipulation() {
+    for (CrushBruteForceTestCase testCase : testCases) {
+      long solutionFound = CrushBruteForce
+          .arrayManipulation(testCase.n, testCase.queries);
+
+      assertEquals(testCase.expected, solutionFound,
+          String.format("%s(%d, %s) answer must be: %s",
+            "CrushBruteForce.arrayManipulation",
+            testCase.n,
+            testCase.queries.toString(),
+            testCase.expected
+          )
+      );
+    }
+  }
+}