AOC so far: days 1, 2, 3

Author: bbycroft

.gitignore

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+.vscode/
+bin/
+obj/

Program.fs

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+// Learn more about F# at http://fsharp.org
+
+open System
+open System.IO
+open System.Text.RegularExpressions;
+
+let readLines fname = File.ReadLines(fname) |> List.ofSeq 
+
+// ==== Day 1 ==== //
+let rec getFirstCumulativeRepeat' vs acc idx seenFreq =
+    match Set.contains acc seenFreq with
+    | true -> acc
+    | false ->
+        let newAcc = acc + (Array.item idx vs)
+        let newIdx = (idx + 1) % Array.length vs
+        getFirstCumulativeRepeat' vs newAcc newIdx (Set.add acc seenFreq)
+
+let getFirstCumulativeRepeat vs = getFirstCumulativeRepeat' vs 0 0 Set.empty
+let day1 () =
+    printfn "Day 1:"
+    let vs = readLines "day1.input" |> List.map Int32.Parse
+    printfn "%d" (List.sum vs)
+    printfn "%d" (getFirstCumulativeRepeat (Array.ofList vs))
+
+// ==== Day 2 ==== //
+let numOfCharInString c s = Seq.length (Seq.filter (fun c' -> c' = c) s)
+let hasRepeat n s = Seq.exists (fun c -> numOfCharInString c s = n) (Set.ofSeq s)
+let numWithN n ss = Seq.filter (hasRepeat n) ss |> Seq.length
+
+let hasOneLetterDifferent (a, b) =
+    Seq.zip a b
+    |> Seq.filter (fun (x, y) -> x <> y)
+    |> Seq.length = 1
+
+let commonLetters (a, b) =
+    Seq.zip a b
+    |> Seq.filter (fun (x, y) -> x = y)
+    |> Seq.map (fun (x, _) -> x)
+
+let day2 () =
+    printfn "Day 2:"
+    let vs = readLines "day2.input"
+    let numWith2 = numWithN 2 vs
+    let numWith3 = numWithN 3 vs
+    printfn "%d * %d = %d" numWith2 numWith3 (numWith2 * numWith3)
+    let product = seq { for a in vs do for b in vs do yield a, b }
+    let result =
+        Seq.find hasOneLetterDifferent product
+        |> commonLetters
+        |> String.Concat
+    printfn "%s" result
+
+// ==== Day 3 ==== //
+
+type Region = { id: string; left: int; top: int; width: int; height: int }
+let parseLine line =
+    let m = Regex.Match(line, @"^#([^ ]+) @ (\d+),(\d+): (\d+)x(\d+)$")
+    let g = m.Groups
+    {
+        id = g.[1].Value
+        left = Int32.Parse g.[2].Value
+        top = Int32.Parse g.[3].Value
+        width = Int32.Parse g.[4].Value
+        height = Int32.Parse g.[5].Value
+    }
+
+let iterRegion size { left=l; top=t; width=w; height=h } = seq {
+    for i in { l .. l + w - 1 } do
+        for j in { t .. t + h - 1 } do
+            yield j * size + i
+    }
+
+let createFabric size regions =
+    let fabric: int[] = Array.zeroCreate (size * size)
+    for region in regions do
+        iterRegion size region |> Seq.iter
+            (fun i -> fabric.[i] <- fabric.[i] + 1)
+    fabric
+
+let countOverlapping fabric =
+    Array.fold (fun count x -> count + (if x > 1 then 1 else 0)) 0 fabric
+
+let regionWithOverlap size (fabric: int[]) region =
+    iterRegion size region |> Seq.forall (fun i -> fabric.[i] = 1)
+
+let day3 () =
+    printfn "Day 3:"
+    let size = 1000 
+    let vs = readLines "day3.input" |> List.map parseLine
+    let fabric = createFabric size vs
+    let numOverlap = countOverlapping fabric
+    printfn "%A" numOverlap
+    let region = List.find (regionWithOverlap size fabric) vs
+    printfn "#%s" region.id
+
+
+[<EntryPoint>]
+let main argv =
+    printfn "Executing main"
+    day1 ()
+    day2 ()
+    day3 ()
+    0

aoc.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="Program.fs" />
+  </ItemGroup>
+
+</Project>