add Problem09

realDuYuanChao · realDuYuanChao · commit 786fd5cc1a0e · 2020-10-05T16:14:43.000+08:00
diff --git a/src/main/java/com/examplehub/projecteuler/Problem09.java b/src/main/java/com/examplehub/projecteuler/Problem09.java
@@ -0,0 +1,27 @@
+package com.examplehub.projecteuler;
+
+/**
+ * A Pythagorean triplet is a set of three natural numbers, a < b < c, for which,
+ * <p>
+ * a^2 + b^2 = c^2
+ * For example, 3^2 + 4^2 = 9 + 16 = 25 = 5^2.
+ * <p>
+ * There exists exactly one Pythagorean triplet for which a + b + c = 1000.
+ * Find the product abc.
+ * <p>
+ * https://projecteuler.net/problem=9
+ */
+public class Problem09 {
+
+    public static int solution1(int n) {
+        for (int a = 1; a <= n; a++) {
+            for (int b = a + 1; b <= n; b++) {
+                int c = n - a - b;
+                if (b < c && (a * a + b * b == c * c)) {
+                    return a * b * c;
+                }
+            }
+        }
+        return -1;
+    }
+}
diff --git a/src/test/java/com/examplehub/projecteuler/Problem09Test.java b/src/test/java/com/examplehub/projecteuler/Problem09Test.java
@@ -0,0 +1,14 @@
+package com.examplehub.projecteuler;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class Problem09Test {
+
+    @Test
+    void testSolution1() {
+        assertEquals(60, Problem09.solution1(12));
+        assertEquals(31875000, Problem09.solution1(1000));
+    }
+}
