[Hacker Rank]: Project Euler #3: Largest prime factor. Solved ✓

algorithm-exercises-java/src/main/java/ae/hackerrank/projecteuler/Euler003.java

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+package ae.hackerrank.projecteuler;
+
+/**
+ * Even Fibonacci numbers.
+ *
+ * @link Problem definition [[docs/hackerrank/projecteuler/euler003.md]]
+ */
+public class Euler003 {
+
+  private Euler003() {}
+
+  private static Long primeFactor(Long n) {
+    if (n < 2) {
+      return null;
+    }
+
+    Long divisor = n;
+    Long maxPrimeFactor = null;
+
+    int i = 2;
+    while (i <= Math.sqrt(divisor)) {
+      if (divisor % i == 0) {
+        divisor = divisor / i;
+        maxPrimeFactor = divisor;
+      } else {
+        i += 1;
+      }
+    }
+
+    if (maxPrimeFactor == null) {
+      return n;
+    }
+
+    return maxPrimeFactor;
+  }
+
+  /**
+   * Even Fibonacci numbers.
+   */
+  public static Long euler003(long n) {
+    return primeFactor(n);
+  }
+}
+
+//CHECKSTYLE.ON: JavadocParagraph

algorithm-exercises-java/src/test/java/ae/hackerrank/projecteuler/Euler003Test.java

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+package ae.hackerrank.projecteuler;
+
+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;
+
+
+@TestInstance(Lifecycle.PER_CLASS)
+class Euler003Test {
+
+  public static class Euler003TestCase {
+    public Long n;
+    public Long expected;
+  }
+
+  private List<Euler003TestCase> testCases;
+
+  @BeforeAll
+  public void setup() throws IOException {
+    String path = String.join("/",
+         "hackerrank",
+        "projecteuler",
+        "euler003.testcases.json");
+
+    this.testCases = JsonLoader.loadJson(path, Euler003TestCase.class);
+  }
+
+  @Test void euler003() {
+
+    for (Euler003TestCase test : testCases) {
+      Long solutionFound = Euler003.euler003(test.n);
+
+      assertEquals(test.expected, solutionFound,
+          "%s(%d) => must be: %s".formatted(
+            "Euler003.euler003",
+            test.n,
+            test.expected
+          )
+      );
+    }
+  }
+}

algorithm-exercises-java/src/test/resources/hackerrank/projecteuler/euler003.testcases.json

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+[
+  { "n": 10, "expected": 5 },
+  { "n": 17, "expected": 17 }
+]