armstrong-numbers: add to track

config.json

@@ -33,6 +33,17 @@
       "unlocked_by": "two-fer",
       "uuid": "2c8afeed-480e-41f3-ad58-590fa8f88029"
     },
+    {
+      "core": false,
+      "difficulty": 2,
+      "slug": "armstrong-numbers",
+      "topics": [
+        "integers",
+        "mathematics"
+      ],
+      "unlocked_by": null,
+      "uuid": "8e1dd48c-e05e-4a72-bf0f-5aed8dd123f5"
+    },
     {
       "core": false,
       "difficulty": 2,

exercises/armstrong-numbers/.meta/src/reference/java/ArmstrongNumbers.java

@@ -0,0 +1,20 @@
+import static java.lang.Math.pow;
+
+class ArmstrongNumbers {
+
+	boolean isArmstrongNumber(int numberToCheck) {
+
+		int number = numberToCheck;
+		int calculation = 0;
+		int length = String.valueOf(number).length();
+
+		while (number > 0) {
+    		calculation += pow((number % 10), length);
+    		number = number / 10;
+		}
+
+		return numberToCheck == calculation;
+
+	}
+
+}

exercises/armstrong-numbers/.meta/version

@@ -0,0 +1 @@
+1.0.0

exercises/armstrong-numbers/README.md

@@ -0,0 +1,30 @@
+# Armstrong Numbers
+
+An [Armstrong number](https://en.wikipedia.org/wiki/Narcissistic_number) is a number that is the sum of its own digits each raised to the power of the number of digits.
+
+For example:
+
+- 9 is an Armstrong number, because `9 = 9^1 = 9`
+- 10 is *not* an Armstrong number, because `10 != 1^2 + 0^2 = 2`
+- 153 is an Armstrong number, because: `153 = 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153`
+- 154 is *not* an Armstrong number, because: `154 != 1^3 + 5^3 + 4^3 = 1 + 125 + 64 = 190`
+
+Write some code to determine whether a number is an Armstrong number.
+
+# Running the tests
+
+You can run all the tests for an exercise by entering
+
+```sh
+$ gradle test
+```
+
+in your terminal.
+
+## Source
+
+Wikipedia [https://en.wikipedia.org/wiki/Narcissistic_number](https://en.wikipedia.org/wiki/Narcissistic_number)
+
+## Submitting Incomplete Solutions
+
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

exercises/armstrong-numbers/build.gradle

@@ -0,0 +1,18 @@
+apply plugin: "java"
+apply plugin: "eclipse"
+apply plugin: "idea"
+
+repositories {
+  mavenCentral()
+}
+
+dependencies {
+  testCompile "junit:junit:4.12"
+}
+
+test {
+  testLogging {
+    exceptionFormat = 'full'
+    events = ["passed", "failed", "skipped"]
+  }
+}

exercises/armstrong-numbers/src/main/java/ArmstrongNumbers.java

@@ -0,0 +1,9 @@
+class ArmstrongNumbers {
+
+	boolean isArmstrongNumber(int numberToCheck) {
+
+		throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+
+	}
+
+}

exercises/armstrong-numbers/src/test/java/ArmstrongNumbersTest.java

@@ -0,0 +1,80 @@
+import org.junit.Before;
+import org.junit.Ignore;
+import org.junit.Test;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertFalse;
+
+public class ArmstrongNumbersTest {
+
+    private ArmstrongNumbers armstrongNumbers;
+
+    @Before
+    public void setup() {
+        armstrongNumbers = new ArmstrongNumbers();
+    }
+
+    @Test
+    public void singleDigitsAreArmstrongNumbers() {
+        int input = 5;
+
+        assertTrue(armstrongNumbers.isArmstrongNumber(input));
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void noTwoDigitArmstrongNumbers() {
+        int input = 10;
+
+        assertFalse(armstrongNumbers.isArmstrongNumber(input));
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void threeDigitNumberIsArmstrongNumber() {
+        int input = 153;
+
+        assertTrue(armstrongNumbers.isArmstrongNumber(input));
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void threeDigitNumberIsNotArmstrongNumber() {
+        int input = 100;
+
+        assertFalse(armstrongNumbers.isArmstrongNumber(input));
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void fourDigitNumberIsArmstrongNumber() {
+        int input = 9474;
+
+        assertTrue(armstrongNumbers.isArmstrongNumber(input));
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void fourDigitNumberIsNotArmstrongNumber() {
+        int input = 9475;
+
+        assertFalse(armstrongNumbers.isArmstrongNumber(input));
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void sevenDigitNumberIsArmstrongNumber() {
+        int input = 9926315;
+
+        assertTrue(armstrongNumbers.isArmstrongNumber(input));
+    }
+
+    @Ignore("Remove to run test")
+    @Test
+    public void sevenDigitNumberIsNotArmstrongNumber() {
+        int input = 9926314;
+
+        assertFalse(armstrongNumbers.isArmstrongNumber(input));
+    }
+
+}

exercises/settings.gradle

@@ -3,6 +3,7 @@ include 'acronym'
 include 'all-your-base'
 include 'allergies'
 include 'anagram'
+include 'armstrong-numbers'
 include 'atbash-cipher'
 include 'bank-account'
 include 'beer-song'