Merge pull request #86 from ErikSchierboom/prime-factors

Add prime-factors exercise

Author: ErikSchierboom

config.json

@@ -56,6 +56,7 @@
     "ocr-numbers",
     "simple-linked-list",
     "robot-simulator",
+    "prime-factors",
     "diamond"
   ],
   "deprecated": [

exercises/prime-factors/Example.fs

@@ -0,0 +1,20 @@
+module PrimeFactors
+
+open System
+
+let possiblePrimes (number: int64): int64 list =
+    [2L; 3L] @ [for n in 6L..6L..number do
+                   for k in [-1L; 1L] do
+                      yield n + k ]
+
+let primeFactorsFor number =
+    let rec loop factors (remainder: int64) (possibleFactors: int64 list) =
+        match possibleFactors with
+        | [] -> factors |> List.rev
+        | factor::xs ->        
+            match remainder with
+            | _ when remainder <= 1L -> factors |> List.rev
+            | _ when remainder % factor = 0L -> loop (factor :: factors) (remainder / factor |> int64) possibleFactors
+            | _ -> loop factors remainder (List.tail possibleFactors)
+
+    loop [] number (possiblePrimes number)

exercises/prime-factors/PrimeFactorsTest.fs

@@ -0,0 +1,54 @@
+module PrimeFactorsTest
+
+open NUnit.Framework
+
+open PrimeFactors
+
+[<Test>]
+let ``Test 1``() =
+    Assert.That(primeFactorsFor 1L, Is.EqualTo([]))
+    
+[<Test>]
+[<Ignore("Remove to run test")>]
+let ``Test 2``() =
+    Assert.That(primeFactorsFor 2L, Is.EqualTo([2]))
+    
+[<Test>]
+[<Ignore("Remove to run test")>]
+let ``Test 3``() =
+    Assert.That(primeFactorsFor 3L, Is.EqualTo([3]))
+
+[<Test>]
+[<Ignore("Remove to run test")>]
+let ``Test 4``() =
+    Assert.That(primeFactorsFor 4L, Is.EqualTo([2; 2]))
+    
+[<Test>]
+[<Ignore("Remove to run test")>]
+let ``Test 6``() =
+    Assert.That(primeFactorsFor 6L, Is.EqualTo([2; 3]))
+    
+[<Test>]
+[<Ignore("Remove to run test")>]
+let ``Test 8``() =
+    Assert.That(primeFactorsFor 8L, Is.EqualTo([2; 2; 2]))
+    
+[<Test>]
+[<Ignore("Remove to run test")>]
+let ``Test 9``() =
+    Assert.That(primeFactorsFor 9L, Is.EqualTo([3; 3]))
+    
+[<Test>]
+[<Ignore("Remove to run test")>]
+let ``Test 27``() =
+    Assert.That(primeFactorsFor 27L, Is.EqualTo([3; 3; 3]))
+    
+[<Test>]
+[<Ignore("Remove to run test")>]
+let ``Test 625``() =
+    Assert.That(primeFactorsFor 625L, Is.EqualTo([5; 5; 5; 5]))
+    
+[<Test>]
+[<Ignore("Remove to run test")>]
+let ``Test 901255``() =
+    Assert.That(primeFactorsFor 901255L, Is.EqualTo([5; 17; 23; 461]))