Day 15

diff --git a/AdventOfCode2017/AdventOfCode2017.fsproj b/AdventOfCode2017/AdventOfCode2017.fsproj
index f2d6bcc..6571eca 100644 (file)
--- a/AdventOfCode2017/AdventOfCode2017.fsproj
+++ b/AdventOfCode2017/AdventOfCode2017.fsproj
@@ -37,6 +37,7 @@
     <PlatformTarget>AnyCPU</PlatformTarget>
     <DocumentationFile>bin\$(Configuration)\$(AssemblyName).XML</DocumentationFile>
     <Prefer32Bit>true</Prefer32Bit>
+    <StartArguments>15</StartArguments>
   </PropertyGroup>
   <PropertyGroup>
     <MinimumVisualStudioVersion Condition="'$(MinimumVisualStudioVersion)' == ''">11</MinimumVisualStudioVersion>

diff --git a/AdventOfCode2017/Day15.fs b/AdventOfCode2017/Day15.fs
index 96bc829..880189d 100644 (file)
--- a/AdventOfCode2017/Day15.fs
+++ b/AdventOfCode2017/Day15.fs
@@ -1,26 +1,23 @@
 module AdventOfCode2017.Day15
 
-let hash = Day10.knotHash2Encoding (fun i -> System.Convert.ToString(i, 2).PadLeft(8, '0'))
+let modulo = 2147483647L
 
-let buildMatrix (input : string) =
-    let mat = Array2D.zeroCreate 128 128
-    for i = 0 to 127 do
-        input + "-" + (string i) |> hash |> Seq.iteri (fun j c -> mat.[i, j] <- int c - int '0')
-    mat
+let generator (factor : int64) (init : int64) : int64 seq =
+    Seq.unfold (
+        fun n ->
+            let n' = n * factor % modulo
+            Some (n', n')
+    ) init
 
-let nbOfUsedSquares (input : string) =
-    let mutable i = 0
-    buildMatrix input |> Array2D.iter (fun b -> i <- i + b)
-    i
+let nbSimilarities genA genB n =
+    Seq.zip genA genB
+    |> Seq.take n
+    |> Seq.fold (fun s (a, b) -> s + if int16 a = int16 b then 1 else 0) 0
 
-let nbOfConnectedRegions (input : string) =
-    let m = buildMatrix input
+let nbSimilarities1 (a : int64) (b : int64) =
+    nbSimilarities (generator 16807L a) (generator 48271L b) 40_000_000
 
-    let rec remove i j =
-        if i >= 0 && i < 128 && j >= 0 && j < 128 && m.[i, j] = 1 then
-            m.[i, j] <- 0
-            1 + remove (i + 1) j * remove (i - 1) j * remove i (j + 1) * remove i (j - 1)
-        else
-            0
-
-    [ for i in 0 .. 127 do for j in 0 .. 127 -> remove i j ] |> List.sum
\ No newline at end of file
+let nbSimilarities2 (a : int64) (b : int64) =
+    let genA = generator 16807L a |> Seq.filter (fun v -> v % 4L = 0L)
+    let genB = generator 48271L b |> Seq.filter (fun v -> v % 8L = 0L)
+    nbSimilarities genA genB 5_000_000
\ No newline at end of file

diff --git a/AdventOfCode2017/Program.fs b/AdventOfCode2017/Program.fs
index 0c6b4de..d69d9bb 100644 (file)
--- a/AdventOfCode2017/Program.fs
+++ b/AdventOfCode2017/Program.fs
@@ -67,8 +67,9 @@ let day14 () =
     sprintf "part1 = %A, part2 = %A" (Day14.nbOfUsedSquares input) (Day14.nbOfConnectedRegions input)
 
 let day15 () =
-    let input = File.ReadAllText "Data/day15.input"
-    sprintf "part1 = %A, part2 = %A" () ()
+    let input = File.ReadAllLines "Data/day15.input"
+    let genA, genB = int64 input.[0], int64 input.[1]
+    sprintf "part1 = %A, part2 = %A" (Day15.nbSimilarities1 genA genB) (Day15.nbSimilarities2 genA genB)
 
 let doDay (n : int) =
     let sw = Diagnostics.Stopwatch ()

diff --git a/Tests/Day15 tests.fs b/Tests/Day15 tests.fs
index cad5296..ffa414f 100644 (file)
--- a/Tests/Day15 tests.fs
+++ b/Tests/Day15 tests.fs
@@ -10,8 +10,10 @@ type ``Day15 tests`` (output : ITestOutputHelper) =
 
     [<Fact>]
     let ``(Part1) From web page`` () =
-        ()
+        let a, b = 65L, 8921L
+        Day15.nbSimilarities1 a b =! 588
 
     [<Fact>]
     let ``(Part2) From web page`` () =
-        ()
\ No newline at end of file
+        let a, b = 65L, 8921L
+        Day15.nbSimilarities2 a b =! 309
\ No newline at end of file