Leetcode 2021.3.23 (examplehub#80)

realDuYuanChao · github-actions · web-flow · commit e4b415bb26e6 · 2021-03-23T09:21:25.000+08:00
* n-th-tribonacci-number

* n-th-tribonacci-number

* Formatted with Google Java Formatter

Co-authored-by: github-actions &lt;${GITHUB_ACTOR}@users.noreply.github.com&gt;
diff --git a/src/main/java/com/examplehub/leetcode/easy/NthTribonacciNumber.java b/src/main/java/com/examplehub/leetcode/easy/NthTribonacciNumber.java
@@ -0,0 +1,27 @@
+package com.examplehub.leetcode.easy;
+
+/** https://leetcode.com/problems/n-th-tribonacci-number/ */
+public class NthTribonacciNumber {
+  public static int solution1(int n) {
+    if (n == 0) {
+      return 0;
+    } else if (n == 1) {
+      return 1;
+    } else if (n == 2) {
+      return 1;
+    } else {
+      return solution1(n - 1) + solution1(n - 2) + solution1(n - 3);
+    }
+  }
+
+  public static int solution2(int n) {
+    int[] nums = new int[n + 3];
+    nums[0] = 0;
+    nums[1] = 1;
+    nums[2] = 1;
+    for (int i = 3; i <= n; ++i) {
+      nums[i] = nums[i - 1] + nums[i - 2] + nums[i - 3];
+    }
+    return nums[n];
+  }
+}
diff --git a/src/test/java/com/examplehub/leetcode/easy/NthTribonacciNumberTest.java b/src/test/java/com/examplehub/leetcode/easy/NthTribonacciNumberTest.java
@@ -0,0 +1,26 @@
+package com.examplehub.leetcode.easy;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+class NthTribonacciNumberTest {
+  @Test
+  void testSolution1() {
+    assertEquals(NthTribonacciNumber.solution1(0), 0);
+    assertEquals(NthTribonacciNumber.solution1(1), 1);
+    assertEquals(NthTribonacciNumber.solution1(2), 1);
+    assertEquals(NthTribonacciNumber.solution1(4), 4);
+    assertEquals(NthTribonacciNumber.solution1(25), 1389537);
+  }
+
+  @Test
+  void testSolution2() {
+    assertEquals(NthTribonacciNumber.solution2(0), 0);
+    assertEquals(NthTribonacciNumber.solution2(1), 1);
+    assertEquals(NthTribonacciNumber.solution2(2), 1);
+    assertEquals(NthTribonacciNumber.solution2(4), 4);
+    assertEquals(NthTribonacciNumber.solution2(25), 1389537);
+    assertEquals(NthTribonacciNumber.solution2(35), 615693474);
+  }
+}
