day14

Author: ia7ck

day14/Program.fs

@@ -1 +1,105 @@
-module Program = let [<EntryPoint>] main _ = 0
+open Xunit
+open FsUnit.Xunit
+
+type Robot = { P: int * int; V: int * int }
+
+type Quadrant =
+    | TopRight
+    | TopLeft
+    | BottomLeft
+    | BottomRight
+
+// x 右
+// y 下
+
+let rec move times w h (robot: Robot) =
+    if times = 0 then
+        robot
+    else
+        let px, py = robot.P
+        let vx, vy = robot.V
+        let newP = (w + px + vx) % w, (h + py + vy) % h
+        move (times - 1) w h { robot with P = newP }
+
+let part1 ((robots, w, h): (Robot seq * int * int)) =
+    let quadratics =
+        robots
+        |> Seq.map (move 100 w h)
+        |> Seq.choose (fun { P = (px, py) } ->
+            if px > w / 2 && py < h / 2 then Some TopRight
+            else if px < w / 2 && py < h / 2 then Some TopLeft
+            else if px < w / 2 && py > h / 2 then Some BottomLeft
+            else if px > w / 2 && py > h / 2 then Some BottomRight
+            else None)
+
+    (1, Seq.countBy id quadratics) ||> Seq.fold (fun acc (_, count) -> acc * count)
+
+let part2 ((robots, w, h): (Robot seq * int * int)) =
+    let rec search elapsed robots =
+        if elapsed >= 1000 then
+            ()
+        else
+            let positions = robots |> Seq.map (fun robot -> robot.P) |> Set.ofSeq
+
+            let map =
+                Array.init h (fun i -> Array.init w (fun j -> if Set.contains (i, j) positions then '@' else ' '))
+
+            printfn "t = %d" elapsed
+            map |> Array.map System.String |> String.concat ("\n") |> printfn "%s"
+            printfn "\n\n\n\n\n"
+
+            search (elapsed + 1) (robots |> Seq.map (move 1 w h))
+
+    search 0 robots
+
+    // この周期でアスキーアートっぽいものが見える
+    // t = 81, 81 + w, 81 + 2w, 81 + 3w, ...
+    // t = 30, 30 + h, 30 + 2h, 30 + 3h, ...
+
+    // 適当な範囲で検索する
+    [ 0..1000 ]
+    |> List.choose (fun p ->
+        // 81 + p * w = 30 + q * h
+        let numQ = (81 - 30) + p * w
+        if numQ % h = 0 then Some(81 + p * w) else None)
+    |> List.head
+
+let parse (input: string) =
+    input.Split("\n")
+    |> Array.map (fun line -> line.Split(" "))
+    |> Array.map (fun line ->
+        let p, v = line[0], line[1]
+        let p = p.Replace("p=", "").Split(",")
+        let v = v.Replace("v=", "").Split(",")
+
+        { P = (int p[0], int p[1])
+          V = (int v[0], int v[1]) })
+
+module Example =
+    let input =
+        "p=0,4 v=3,-3
+p=6,3 v=-1,-3
+p=10,3 v=-1,2
+p=2,0 v=2,-1
+p=0,0 v=1,3
+p=3,0 v=-2,-2
+p=7,6 v=-1,-3
+p=3,0 v=-1,-2
+p=9,3 v=2,3
+p=7,3 v=-1,2
+p=2,4 v=2,-3
+p=9,5 v=-3,-3"
+
+    [<Fact>]
+    let testPart1 () =
+        (parse input, 7, 11) |> part1 |> should equal 12
+
+[<EntryPoint>]
+let main _ =
+    let input = stdin.ReadToEnd().TrimEnd()
+    let robots = parse input
+
+    (robots, 101, 103) |> part1 |> printfn "Part 1: %d"
+    (robots, 101, 103) |> part2 |> printfn "Part 2: %d"
+
+    0

day14/Tests.fs

@@ -9,7 +9,6 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <Compile Include="Tests.fs" />
     <Compile Include="Program.fs" />
   </ItemGroup>