Add perfect-numbers (#333)

Author: BNAndras

config.json

@@ -335,6 +335,14 @@
           "math"
         ]
       },
+      {
+        "slug": "perfect-numbers",
+        "name": "Perfect Numbers",
+        "uuid": "6f95df06-8171-44a6-8fb3-d43951b9fae3",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "phone-number",
         "name": "Phone Number",

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

@@ -0,0 +1,39 @@
+# Instructions
+
+Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for positive integers.
+
+The Greek mathematician [Nicomachus][nicomachus] devised a classification scheme for positive integers, identifying each as belonging uniquely to the categories of [perfect](#perfect), [abundant](#abundant), or [deficient](#deficient) based on their [aliquot sum][aliquot-sum].
+The _aliquot sum_ is defined as the sum of the factors of a number not including the number itself.
+For example, the aliquot sum of `15` is `1 + 3 + 5 = 9`.
+
+## Perfect
+
+A number is perfect when it equals its aliquot sum.
+For example:
+
+- `6` is a perfect number because `1 + 2 + 3 = 6`
+- `28` is a perfect number because `1 + 2 + 4 + 7 + 14 = 28`
+
+## Abundant
+
+A number is abundant when it is less than its aliquot sum.
+For example:
+
+- `12` is an abundant number because `1 + 2 + 3 + 4 + 6 = 16`
+- `24` is an abundant number because `1 + 2 + 3 + 4 + 6 + 8 + 12 = 36`
+
+## Deficient
+
+A number is deficient when it is greater than its aliquot sum.
+For example:
+
+- `8` is a deficient number because `1 + 2 + 4 = 7`
+- Prime numbers are deficient
+
+## Task
+
+Implement a way to determine whether a given number is [perfect](#perfect).
+Depending on your language track, you may also need to implement a way to determine whether a given number is [abundant](#abundant) or [deficient](#deficient).
+
+[nicomachus]: https://en.wikipedia.org/wiki/Nicomachus
+[aliquot-sum]: https://en.wikipedia.org/wiki/Aliquot_sum

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

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "perfect-numbers.coffee"
+    ],
+    "test": [
+      "perfect-numbers.spec.coffee"
+    ],
+    "example": [
+      ".meta/example.coffee"
+    ]
+  },
+  "blurb": "Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for positive integers.",
+  "source": "Taken from Chapter 2 of Functional Thinking by Neal Ford.",
+  "source_url": "https://www.oreilly.com/library/view/functional-thinking/9781449365509/"
+}

exercises/practice/perfect-numbers/.meta/example.coffee

@@ -0,0 +1,18 @@
+class PerfectNumbers
+  @classify: (number) ->
+    if number <= 0
+      throw new Error 'Classification is only possible for positive integers.'
+    
+    sum = 0
+    for i in [1...number]
+      if number % i == 0
+        sum += i
+    
+    if sum < number
+      'deficient'
+    else if sum > number
+      'abundant'
+    else
+      'perfect'
+
+module.exports = PerfectNumbers

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

@@ -0,0 +1,49 @@
+# 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.
+
+[163e8e86-7bfd-4ee2-bd68-d083dc3381a3]
+description = "Perfect numbers -> Smallest perfect number is classified correctly"
+
+[169a7854-0431-4ae0-9815-c3b6d967436d]
+description = "Perfect numbers -> Medium perfect number is classified correctly"
+
+[ee3627c4-7b36-4245-ba7c-8727d585f402]
+description = "Perfect numbers -> Large perfect number is classified correctly"
+
+[80ef7cf8-9ea8-49b9-8b2d-d9cb3db3ed7e]
+description = "Abundant numbers -> Smallest abundant number is classified correctly"
+
+[3e300e0d-1a12-4f11-8c48-d1027165ab60]
+description = "Abundant numbers -> Medium abundant number is classified correctly"
+
+[ec7792e6-8786-449c-b005-ce6dd89a772b]
+description = "Abundant numbers -> Large abundant number is classified correctly"
+
+[e610fdc7-2b6e-43c3-a51c-b70fb37413ba]
+description = "Deficient numbers -> Smallest prime deficient number is classified correctly"
+
+[0beb7f66-753a-443f-8075-ad7fbd9018f3]
+description = "Deficient numbers -> Smallest non-prime deficient number is classified correctly"
+
+[1c802e45-b4c6-4962-93d7-1cad245821ef]
+description = "Deficient numbers -> Medium deficient number is classified correctly"
+
+[47dd569f-9e5a-4a11-9a47-a4e91c8c28aa]
+description = "Deficient numbers -> Large deficient number is classified correctly"
+
+[a696dec8-6147-4d68-afad-d38de5476a56]
+description = "Deficient numbers -> Edge case (no factors other than itself) is classified correctly"
+
+[72445cee-660c-4d75-8506-6c40089dc302]
+description = "Invalid inputs -> Zero is rejected (as it is not a positive integer)"
+
+[2d72ce2c-6802-49ac-8ece-c790ba3dae13]
+description = "Invalid inputs -> Negative integer is rejected (as it is not a positive integer)"

exercises/practice/perfect-numbers/perfect-numbers.coffee

@@ -0,0 +1,4 @@
+class PerfectNumbers
+  @classify: (number) ->
+
+module.exports = PerfectNumbers

exercises/practice/perfect-numbers/perfect-numbers.spec.coffee

@@ -0,0 +1,49 @@
+PerfectNumbers = require './perfect-numbers'
+
+describe 'Perfect Numbers', ->
+  describe 'Perfect numbers', ->
+    it 'Smallest perfect number is classified correctly', ->
+      expect(PerfectNumbers.classify(6)).toEqual 'perfect'
+
+    xit 'Medium perfect number is classified correctly', ->
+      expect(PerfectNumbers.classify(28)).toEqual 'perfect'
+
+    xit 'Large perfect number is classified correctly', ->
+      expect(PerfectNumbers.classify(33550336)).toEqual 'perfect'
+
+  describe 'Abundant numbers', ->
+    xit 'Smallest abundant number is classified correctly', ->
+      expect(PerfectNumbers.classify(12)).toEqual 'abundant'
+
+    xit 'Medium abundant number is classified correctly', ->
+      expect(PerfectNumbers.classify(30)).toEqual 'abundant'
+
+    xit 'Large abundant number is classified correctly', ->
+      expect(PerfectNumbers.classify(33550335)).toEqual 'abundant'
+
+  describe 'Deficient numbers', ->
+    xit 'Smallest prime deficient number is classified correctly', ->
+      expect(PerfectNumbers.classify(2)).toEqual 'deficient'
+
+    xit 'Smallest non-prime deficient number is classified correctly', ->
+      expect(PerfectNumbers.classify(4)).toEqual 'deficient'
+
+    xit 'Medium deficient number is classified correctly', ->
+      expect(PerfectNumbers.classify(32)).toEqual 'deficient'
+
+    xit 'Large deficient number is classified correctly', ->
+      expect(PerfectNumbers.classify(33550337)).toEqual 'deficient'
+
+    xit 'Edge case (no factors other than itself) is classified correctly', ->
+      expect(PerfectNumbers.classify(1)).toEqual 'deficient'
+    
+  describe 'Invalid inputs', ->
+    xit 'Zero is rejected (as it is not a positive integer)', ->
+      expect ->
+        PerfectNumbers.classify(0)
+      .toThrow new Error('Classification is only possible for positive integers.')
+    
+    xit 'Negative integer is rejected (as it is not a positive integer)', ->
+      expect ->
+        PerfectNumbers.classify(-1)
+      .toThrow new Error('Classification is only possible for positive integers.')