add lucas number

realDuYuanChao · realDuYuanChao · commit da5628faef74 · 2020-10-26T09:49:26.000+08:00
diff --git a/src/main/java/com/examplehub/maths/LucasNumbersIteration.java b/src/main/java/com/examplehub/maths/LucasNumbersIteration.java
@@ -0,0 +1,25 @@
+package com.examplehub.maths;
+
+/** https://en.wikipedia.org/wiki/Lucas_number */
+public class LucasNumbersIteration {
+
+  /**
+   * Get nth lucas number using iteration.
+   *
+   * @param n the nth.
+   * @return nth lucas number.
+   */
+  public static int lucas(int n) {
+    if (n == 0) {
+      return 2;
+    }
+    int first = 1;
+    int second = 3;
+    for (int i = 1; i < n; i++) {
+      int temp = first + second;
+      first = second;
+      second = temp;
+    }
+    return first;
+  }
+}
diff --git a/src/test/java/com/examplehub/maths/LucasNumbersIterationTest.java b/src/test/java/com/examplehub/maths/LucasNumbersIterationTest.java
@@ -0,0 +1,15 @@
+package com.examplehub.maths;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class LucasNumbersIterationTest {
+  @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], LucasNumbersIteration.lucas(i));
+    }
+  }
+}
