From e56fcf9023ba43919cae20393a2b85d89206271c Mon Sep 17 00:00:00 2001
From: Haidong Ji
Date: Sun, 19 Aug 2018 10:24:13 -0500
Subject: GCD done!

Interesting. The original code was like this:
	public static int getGCD(int a, int b) {
		if (b == 0) {
			return a;
		}

		if (b > a) {
			return getGCD(b, b % a);
		} else {
			return getGCD(b, a % b);
		}
	}
And it failed the test of 14159572, 63967072. After chaning the code to:
	public static int getGCD(int a, int b) {
		if (b == 0) {
			return a;
		}

		if (b > a) {
			return getGCD(b, a);
		} else {
			return getGCD(b, a % b);
		}
	}
It worked! I guess it's important to do a pretty exhaustive testing to
find this subtle bug---
 AlgoDesignAndTechniqueEdxJava/sources/GCD.java   | 24 +++++++++++++++++
 AlgoDesignAndTechniqueEdxJava/tests/GCDTest.java | 33 ++++++++++++++++++++++++
 2 files changed, 57 insertions(+)
 create mode 100644 AlgoDesignAndTechniqueEdxJava/sources/GCD.java
 create mode 100644 AlgoDesignAndTechniqueEdxJava/tests/GCDTest.java

diff --git a/AlgoDesignAndTechniqueEdxJava/sources/GCD.java b/AlgoDesignAndTechniqueEdxJava/sources/GCD.java
new file mode 100644
index 0000000..5e29e4f
--- /dev/null
+++ b/AlgoDesignAndTechniqueEdxJava/sources/GCD.java
@@ -0,0 +1,24 @@
+import java.util.Scanner;
+
+public class GCD {
+
+	public static int getGCD(int a, int b) {
+		if (b == 0) {
+			return a;
+		}
+
+		if (b > a) {
+			return getGCD(b, a);
+		} else {
+			return getGCD(b, a % b);
+		}
+	}
+
+	public static void main(String args[]) {
+		Scanner in = new Scanner(System.in);
+		int a = in.nextInt();
+		int b = in.nextInt();
+
+		System.out.println(getGCD(a, b));
+	}
+}
diff --git a/AlgoDesignAndTechniqueEdxJava/tests/GCDTest.java b/AlgoDesignAndTechniqueEdxJava/tests/GCDTest.java
new file mode 100644
index 0000000..1c8fedd
--- /dev/null
+++ b/AlgoDesignAndTechniqueEdxJava/tests/GCDTest.java
@@ -0,0 +1,33 @@
+import static org.junit.jupiter.api.Assertions.*;
+import org.junit.jupiter.api.Test;
+
+public class GCDTest {
+	@Test
+	void testGCD1() {
+		assertEquals(1, GCD.getGCD(18, 35));
+	}
+	@Test
+	void testGCD2() {
+		assertEquals(17657, GCD.getGCD(28851538, 1183019));
+	}
+
+	@Test
+	void testGCD3() {
+		assertEquals(7, GCD.getGCD(1344, 217));
+	}
+
+	@Test
+	void testGCD4() {
+		assertEquals(1344, GCD.getGCD(1344, 1344));
+	}
+
+	@Test
+	void testGCD5() {
+		assertEquals(4, GCD.getGCD(14159572, 63967072));
+	}
+
+	@Test
+	void testGCD6() {
+		assertEquals(4, GCD.getGCD(63967072,14159572));
+	}
+}
-- 
cgit v1.2.3