From c39940584097f4a8173e86aaed04752a0947e929 Mon Sep 17 00:00:00 2001
From: U7112358 <u7112358@anu.edu.au>
Date: Sun, 30 Oct 2022 22:12:11 +1100
Subject: [PATCH 1/2] Added Armstrong number algorithm and tests for it

---
 .../algorithms/math/ArmstrongNumber.java      | 23 +++++++++++++++++++
 .../algorithms/math/ArmstrongNumberTest.java  | 19 +++++++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 src/main/java/com/williamfiset/algorithms/math/ArmstrongNumber.java
 create mode 100644 src/test/java/com/williamfiset/algorithms/math/ArmstrongNumberTest.java

diff --git a/src/main/java/com/williamfiset/algorithms/math/ArmstrongNumber.java b/src/main/java/com/williamfiset/algorithms/math/ArmstrongNumber.java
new file mode 100644
index 000000000..ceefd9538
--- /dev/null
+++ b/src/main/java/com/williamfiset/algorithms/math/ArmstrongNumber.java
@@ -0,0 +1,23 @@
+package com.williamfiset.algorithms.math;
+
+public class ArmstrongNumber {
+    /*
+     * An Armstrong number is the one where
+     * the sum of each digit of the number to the
+     * power of number of the digits in that number
+     * will be equal to that number for example
+     * 153 (n = 3 digits) is equal to:
+     * 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153
+     */
+    public static boolean isArmstrongNumber(int number){
+        int numberLength = (String.valueOf(number)).length();
+        int tracker = number;
+        int answer = 0;
+        while (tracker !=0){
+            int lastDigit = (int) tracker % 10;
+            answer = answer + (int) Math.pow(lastDigit , numberLength);
+            tracker = Math.floorDiv(tracker , 10);
+        }
+        return (answer == number);
+    }
+}
diff --git a/src/test/java/com/williamfiset/algorithms/math/ArmstrongNumberTest.java b/src/test/java/com/williamfiset/algorithms/math/ArmstrongNumberTest.java
new file mode 100644
index 000000000..8ec08ce4f
--- /dev/null
+++ b/src/test/java/com/williamfiset/algorithms/math/ArmstrongNumberTest.java
@@ -0,0 +1,19 @@
+package com.williamfiset.algorithms.math;
+
+import static com.williamfiset.algorithms.math.ArmstrongNumber.isArmstrongNumber;
+import static org.junit.jupiter.api.Assertions.*;
+import org.junit.*;
+
+
+public class ArmstrongNumberTest {
+    @Test
+    public void armstrongNumberTest(){
+        assertTrue(isArmstrongNumber(1)==true);
+        assertTrue(isArmstrongNumber(153)==true);
+        assertTrue(isArmstrongNumber(1634)==true);
+        assertTrue(isArmstrongNumber(371)==true);
+        assertFalse(isArmstrongNumber(10)==true);
+        assertFalse(isArmstrongNumber(100)==true);
+        assertFalse(isArmstrongNumber(1000)==true);
+    }
+}
\ No newline at end of file

From 0b9e5a0161c3673718cefccdd89f6f64e5852ad8 Mon Sep 17 00:00:00 2001
From: U7112358 <u7112358@anu.edu.au>
Date: Sun, 30 Oct 2022 23:23:52 +1100
Subject: [PATCH 2/2] #338 added standard deviation and tests for it

---
 .../algorithms/math/StandardDeviation.java    | 17 +++++++++++++++++
 .../math/StandardDeviationTest.java           | 19 +++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 src/main/java/com/williamfiset/algorithms/math/StandardDeviation.java
 create mode 100644 src/test/java/com/williamfiset/algorithms/math/StandardDeviationTest.java

diff --git a/src/main/java/com/williamfiset/algorithms/math/StandardDeviation.java b/src/main/java/com/williamfiset/algorithms/math/StandardDeviation.java
new file mode 100644
index 000000000..cbe73efce
--- /dev/null
+++ b/src/main/java/com/williamfiset/algorithms/math/StandardDeviation.java
@@ -0,0 +1,17 @@
+package com.williamfiset.algorithms.math;
+
+public class StandardDeviation {
+
+    public static double SD(double arr[]) {
+        double sum = 0, StandardDeviation = 0;
+        int length = arr.length;
+        for (double num : arr) {
+            sum += num;
+        }
+        double mean = sum / length;
+        for (double num : arr) {
+            StandardDeviation = StandardDeviation + Math.pow(num - mean, 2);
+        }
+        return Math.sqrt((StandardDeviation / length));
+    }
+}
diff --git a/src/test/java/com/williamfiset/algorithms/math/StandardDeviationTest.java b/src/test/java/com/williamfiset/algorithms/math/StandardDeviationTest.java
new file mode 100644
index 000000000..255c780b9
--- /dev/null
+++ b/src/test/java/com/williamfiset/algorithms/math/StandardDeviationTest.java
@@ -0,0 +1,19 @@
+package com.williamfiset.algorithms.math;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.Test;
+public class StandardDeviationTest {
+
+    @Test
+    public void StandardDeviation4(){
+        double[] array = {-1, -2, -3, -4, -5};
+        double result = StandardDeviation.SD(array);
+        assertEquals(1.4142135623730951, result);
+    }
+
+    @Test
+    public void StandardDeviation2(){
+        double[] array = {3, 5, 7, 20, 55, 12, 1, 3, 5, 4};
+        double result = StandardDeviation.SD(array);
+        assertEquals(15.428869044748549, result);
+    }
+}