add problem 20

realDuYuanChao · realDuYuanChao · commit 874144da501e · 2020-10-07T14:13:32.000+08:00
diff --git a/src/main/java/com/examplehub/maths/SumOfDigits.java b/src/main/java/com/examplehub/maths/SumOfDigits.java
@@ -8,7 +8,7 @@ public class SumOfDigits {
      * @param number the number.
      * @return the sum of digits.
      */
-    public static int sumOfDigits(int number) {
+    public static int sumOfDigits(long number) {
         number = Math.abs(number);
         int sum = 0;
         while (number != 0) {
diff --git a/src/main/java/com/examplehub/projecteuler/Problem20.java b/src/main/java/com/examplehub/projecteuler/Problem20.java
@@ -0,0 +1,10 @@
+package com.examplehub.projecteuler;
+
+import com.examplehub.maths.Factorial;
+import com.examplehub.maths.SumOfDigits;
+
+public class Problem20 {
+    public static int solution1(int number) {
+        return SumOfDigits.sumOfDigits(Factorial.factorial(number));
+    }
+}
diff --git a/src/test/java/com/examplehub/projecteuler/Problem20Test.java b/src/test/java/com/examplehub/projecteuler/Problem20Test.java
@@ -0,0 +1,13 @@
+package com.examplehub.projecteuler;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class Problem20Test {
+
+    @Test
+    void test() {
+        assertEquals(27, Problem20.solution1(10));
+    }
+}
