[Hacker Rank] Interview Preparation Kit: Miscellaneous: Flipping bits. New way to solve ✅.

Gonzalo Diaz · Gonzalo Diaz · commit 521a9368ef08 · 2025-07-21T12:05:55.000-04:00
diff --git a/algorithm-exercises-java/src/main/java/ae/hackerrank/interview_preparation_kit/miscellaneous/FlippingBitsAlternative.java b/algorithm-exercises-java/src/main/java/ae/hackerrank/interview_preparation_kit/miscellaneous/FlippingBitsAlternative.java
@@ -0,0 +1,19 @@
+package ae.hackerrank.interview_preparation_kit.miscellaneous;
+
+/**
+ * AngryFlorist.
+ *
+ * @link Problem definition
+ *       [[docs/hackerrank/interview_preparation_kit/miscellaneous/flipping-bits.md]]
+ */
+public class FlippingBitsAlternative {
+
+  private FlippingBitsAlternative() {}
+
+  /**
+   * flippingBits.
+   */
+  public static long flippingBits(long n) {
+    return ~n & 0xFFFFFFFFL; // Use bitwise NOT and mask to ensure 32-bit unsigned result
+  }
+}
diff --git a/algorithm-exercises-java/src/test/java/ae/hackerrank/interview_preparation_kit/miscellaneous/FlippingBitsTestAlternativeTest.java b/algorithm-exercises-java/src/test/java/ae/hackerrank/interview_preparation_kit/miscellaneous/FlippingBitsTestAlternativeTest.java
@@ -0,0 +1,61 @@
+package ae.hackerrank.interview_preparation_kit.miscellaneous;
+
+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;
+
+/**
+ * FlippingBitsTflippingBits.
+ */
+@TestInstance(Lifecycle.PER_CLASS)
+class FlippingBitsTestAlternativeTest {
+  /**
+   * FlippingBitsTestAlternativeTestCaseTest.
+   */
+  public static class FlippingBitsTestAlternativeTestCaseTest {
+    public long input;
+    public long answer;
+  }
+
+  /**
+   * FlippingBitsTestAlternativeTestCase.
+   */
+  public static class FlippingBitsTestAlternativeTestCase {
+    public String title;
+    public List<FlippingBitsTestAlternativeTestCaseTest> tests;
+  }
+
+  private List<FlippingBitsTestAlternativeTestCase> testCases;
+
+  @BeforeAll
+  void setup() throws IOException {
+    String path = String.join("/",
+        "hackerrank",
+        "interview_preparation_kit",
+        "miscellaneous",
+        "flipping_bits.testcases.json");
+
+    this.testCases = JsonLoader.loadJson(path, FlippingBitsTestAlternativeTestCase.class);
+  }
+
+  @Test
+  void testLuckBalance() {
+    for (FlippingBitsTestAlternativeTestCase tests : testCases) {
+      for (FlippingBitsTestAlternativeTestCaseTest test : tests.tests) {
+        Long result = FlippingBitsAlternative.flippingBits(test.input);
+
+        assertEquals(test.answer, result,
+            "%s(%s) => must be: %d".formatted(
+              "FlippingBits.flippingBits",
+              test.input,
+              test.answer));
+      }
+    }
+  }
+}
