[Hacker Rank] Interview Preparation Kit: Dictionaries and Hashmaps: Count Triplets. Brute force solution added.

Author: Gonzalo Diaz

algorithm-exercises-java/src/main/java/ae/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/CountTripletsBruteForce.java

@@ -0,0 +1,38 @@
+package ae.hackerrank.interview_preparation_kit.dictionaries_and_hashmaps;
+
+import java.util.List;
+
+/**
+ * CountTripletsBruteForce.
+ *
+ * @link Problem definition
+ *       [[docs/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/count_triplets_1.md/]]
+ *
+ * @see CountTriplets
+ */
+public class CountTripletsBruteForce {
+  private CountTripletsBruteForce() {
+  }
+
+  /**
+   * CountTriples.
+   */
+  static long countTriplets(List<Long> arr, long r) {
+
+    long size = arr.size();
+    long counter = 0L;
+
+    for (int i = 0; i < size - 2; i++) {
+      for (int j = i + 1; j < size - 1; j++) {
+        for (int k = j + 1; k < size; k++) {
+
+          if (r * arr.get(i) == arr.get(j) && r * arr.get(j) == arr.get(k)) {
+            counter += 1;
+          }
+        }
+      }
+    }
+
+    return counter;
+  }
+}

algorithm-exercises-java/src/test/java/ae/hackerrank/interview_preparation_kit/dictionaries_and_hashmaps/CountTripletsBruteForceTest.java

@@ -0,0 +1,52 @@
+package ae.hackerrank.interview_preparation_kit.dictionaries_and_hashmaps;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+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;
+import util.JsonLoader;
+
+/**
+ * CountTripletsBruteForceTest.
+ */
+@TestInstance(Lifecycle.PER_CLASS)
+class CountTripletsBruteForceTest {
+  public static class CountTripletsBruteForceTestCase {
+    public String title;
+    public List<Long> input;
+    public Long r;
+    public Long expected;
+  }
+
+  private List<CountTripletsBruteForceTestCase> smallTestCases;
+
+  @BeforeAll
+  void setup() throws IOException {
+    String path;
+    path = String.join("/",
+        "hackerrank",
+        "interview_preparation_kit",
+        "dictionaries_and_hashmaps",
+        "count_triplets_1.small.testcases.json");
+
+    this.smallTestCases = JsonLoader.loadJson(path, CountTripletsBruteForceTestCase.class);
+  }
+
+  @Test
+  void testCountTriplets() {
+    for (CountTripletsBruteForceTestCase test : smallTestCases) {
+      Long solutionFound = CountTripletsBruteForce.countTriplets(test.input, test.r);
+
+      assertEquals(test.expected, solutionFound,
+          "%s(%s, %d) answer must be: %d".formatted(
+              "CountTripletsBruteForce.countTriplets",
+              test.input.toString(),
+              test.r,
+              test.expected));
+    }
+  }
+}