add lucas number

realDuYuanChao · realDuYuanChao · commit 247914a912e4 · 2020-10-26T09:34:47.000+08:00
diff --git a/src/main/java/com/examplehub/maths/LucasNumbers.java b/src/main/java/com/examplehub/maths/LucasNumbers.java
@@ -0,0 +1,17 @@
+package com.examplehub.maths;
+
+/**
+ * https://en.wikipedia.org/wiki/Lucas_number
+ */
+public class LucasNumbers {
+
+  /**
+   * Get nth lucas number.
+   *
+   * @param n the nth.
+   * @return nth lucas number.
+   */
+  public static int lucas(int n) {
+    return n == 0 ? 2 : n == 1 ? 1 : lucas(n - 1) + lucas(n - 2);
+  }
+}
diff --git a/src/test/java/com/examplehub/maths/LucasNumbersTest.java b/src/test/java/com/examplehub/maths/LucasNumbersTest.java
@@ -0,0 +1,15 @@
+package com.examplehub.maths;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class LucasNumbersTest {
+  @Test
+  void test() {
+    int[] lucasNumbers = {2, 1, 3, 4, 7, 11, 18, 29, 47, 76, 123};
+    for (int i = 0; i < lucasNumbers.length; i++) {
+      assertEquals(lucasNumbers[i], LucasNumbers.lucas(i));
+    }
+  }
+}
