[New Exercise]: Armstrong Numbers (#708)

* Add Armstrong Numbers exercise

* Add author

Author: meatball133

config.json

@@ -432,6 +432,14 @@
           "transforming"
         ]
       },
+      {
+        "slug": "armstrong-numbers",
+        "name": "Armstrong Numbers",
+        "uuid": "6bd76515-cc17-4238-bc08-7fbdfea14131",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "grade-school",
         "name": "Grade School",

exercises/practice/armstrong-numbers/.docs/instructions.md

@@ -0,0 +1,14 @@
+# Instructions
+
+An [Armstrong number][armstrong-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 = 1`
+- 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.
+
+[armstrong-number]: https://en.wikipedia.org/wiki/Narcissistic_number

exercises/practice/armstrong-numbers/.meta/Sources/ArmstrongNumbers/ArmstrongNumbersExample.swift

@@ -0,0 +1,8 @@
+import Foundation
+
+func isArmstrongNumber(_ number: Int) -> Bool {
+    let stringNumber = String(number)
+    let numberLength = stringNumber.count
+    let sum = stringNumber.compactMap { Int(String($0)) }.reduce(0) { $0 + Int(pow(Double($1), Double(numberLength))) }
+    return sum == number
+}

exercises/practice/armstrong-numbers/.meta/config.json

@@ -0,0 +1,17 @@
+{
+  "authors": ["meatball133"],
+  "files": {
+    "solution": [
+      "Sources/ArmstrongNumbers/ArmstrongNumbers.swift"
+    ],
+    "test": [
+      "Tests/ArmstrongNumbersTests/ArmstrongNumbersTests.swift"
+    ],
+    "example": [
+      ".meta/Sources/ArmstrongNumbers/ArmstrongNumbersExample.swift"
+    ]
+  },
+  "blurb": "Determine if a number is an Armstrong number.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Narcissistic_number"
+}

exercises/practice/armstrong-numbers/.meta/template.swift

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+import XCTest
+@testable import {{exercise|camelCase}}
+class {{exercise|camelCase}}Tests: XCTestCase {
+    let runAll = Bool(ProcessInfo.processInfo.environment["RUNALL", default: "false"]) ?? false
+
+    {% for case in cases %}
+    {% if forloop.first -%}
+        func test{{case.description |camelCase }}() {
+    {% else -%}
+        func test{{case.description |camelCase }}() throws {
+        try XCTSkipIf(true && !runAll) // change true to false to run this test
+    {% endif -%}
+        {%- if case.expected -%}
+        XCTAssertTrue(isArmstrongNumber({{case.input.number}}))
+        {%- else -%}
+        XCTAssertFalse(isArmstrongNumber({{case.input.number}}))
+        {%- endif %}
+    }
+    {% endfor -%}
+}

exercises/practice/armstrong-numbers/.meta/tests.toml

@@ -0,0 +1,45 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[c1ed103c-258d-45b2-be73-d8c6d9580c7b]
+description = "Zero is an Armstrong number"
+
+[579e8f03-9659-4b85-a1a2-d64350f6b17a]
+description = "Single-digit numbers are Armstrong numbers"
+
+[2d6db9dc-5bf8-4976-a90b-b2c2b9feba60]
+description = "There are no two-digit Armstrong numbers"
+
+[509c087f-e327-4113-a7d2-26a4e9d18283]
+description = "Three-digit number that is an Armstrong number"
+
+[7154547d-c2ce-468d-b214-4cb953b870cf]
+description = "Three-digit number that is not an Armstrong number"
+
+[6bac5b7b-42e9-4ecb-a8b0-4832229aa103]
+description = "Four-digit number that is an Armstrong number"
+
+[eed4b331-af80-45b5-a80b-19c9ea444b2e]
+description = "Four-digit number that is not an Armstrong number"
+
+[f971ced7-8d68-4758-aea1-d4194900b864]
+description = "Seven-digit number that is an Armstrong number"
+
+[7ee45d52-5d35-4fbd-b6f1-5c8cd8a67f18]
+description = "Seven-digit number that is not an Armstrong number"
+
+[5ee2fdf8-334e-4a46-bb8d-e5c19c02c148]
+description = "Armstrong number containing seven zeroes"
+include = false
+
+[12ffbf10-307a-434e-b4ad-c925680e1dd4]
+description = "The largest and last Armstrong number"
+include = false

exercises/practice/armstrong-numbers/Package.swift

@@ -0,0 +1,21 @@
+// swift-tools-version:5.3
+
+import PackageDescription
+
+let package = Package(
+  name: "ArmstrongNumbers",
+  products: [
+    .library(
+      name: "ArmstrongNumbers",
+      targets: ["ArmstrongNumbers"])
+  ],
+  dependencies: [],
+  targets: [
+    .target(
+      name: "ArmstrongNumbers",
+      dependencies: []),
+    .testTarget(
+      name: "ArmstrongNumbersTests",
+      dependencies: ["ArmstrongNumbers"]),
+  ]
+)

exercises/practice/armstrong-numbers/Sources/ArmstrongNumbers/ArmstrongNumbers.swift

@@ -0,0 +1,3 @@
+func isArmstrongNumber(_ number: Int) -> Bool {
+    // Write your code for the 'Armstrong Numbers' exercise here.
+}

exercises/practice/armstrong-numbers/Tests/ArmstrongNumbersTests/ArmstrongNumbersTests.swift

@@ -0,0 +1,51 @@
+import XCTest
+
+@testable import ArmstrongNumbers
+
+class ArmstrongNumbersTests: XCTestCase {
+  let runAll = Bool(ProcessInfo.processInfo.environment["RUNALL", default: "false"]) ?? false
+
+  func testZeroIsAnArmstrongNumber() {
+    XCTAssertTrue(isArmstrongNumber(0))
+  }
+
+  func testSingleDigitNumbersAreArmstrongNumbers() throws {
+    try XCTSkipIf(true && !runAll)  // change true to false to run this test
+    XCTAssertTrue(isArmstrongNumber(5))
+  }
+
+  func testThereAreNoTwoDigitArmstrongNumbers() throws {
+    try XCTSkipIf(true && !runAll)  // change true to false to run this test
+    XCTAssertFalse(isArmstrongNumber(10))
+  }
+
+  func testThreeDigitNumberThatIsAnArmstrongNumber() throws {
+    try XCTSkipIf(true && !runAll)  // change true to false to run this test
+    XCTAssertTrue(isArmstrongNumber(153))
+  }
+
+  func testThreeDigitNumberThatIsNotAnArmstrongNumber() throws {
+    try XCTSkipIf(true && !runAll)  // change true to false to run this test
+    XCTAssertFalse(isArmstrongNumber(100))
+  }
+
+  func testFourDigitNumberThatIsAnArmstrongNumber() throws {
+    try XCTSkipIf(true && !runAll)  // change true to false to run this test
+    XCTAssertTrue(isArmstrongNumber(9474))
+  }
+
+  func testFourDigitNumberThatIsNotAnArmstrongNumber() throws {
+    try XCTSkipIf(true && !runAll)  // change true to false to run this test
+    XCTAssertFalse(isArmstrongNumber(9475))
+  }
+
+  func testSevenDigitNumberThatIsAnArmstrongNumber() throws {
+    try XCTSkipIf(true && !runAll)  // change true to false to run this test
+    XCTAssertTrue(isArmstrongNumber(9_926_315))
+  }
+
+  func testSevenDigitNumberThatIsNotAnArmstrongNumber() throws {
+    try XCTSkipIf(true && !runAll)  // change true to false to run this test
+    XCTAssertFalse(isArmstrongNumber(9_926_314))
+  }
+}