Day 5 Part 1

Day5.fs

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+namespace Adventofcode2021
+
+module Day5 =
+
+    open System.Collections.Generic
+    open System.Linq
+
+    [<Literal>]
+    let InputFile = "Day5Input.txt"
+
+    type Line = { Start: int * int; End: int * int }
+
+    let parseLine (s: string) =
+        let regex = System.Text.RegularExpressions.Regex(@"(\d+),(\d+) -> (\d+),(\d+)")
+        let matches = regex.Matches s
+
+        { Start = int matches.[0].Groups.[1].Value, int matches.[0].Groups.[2].Value
+          End = int matches.[0].Groups.[3].Value, int matches.[0].Groups.[4].Value }
+
+    let isHorizontalOrVertical { Start = x1, y1; End = x2, y2 } = x1 = x2 || y1 = y2
+
+    let countOverlapPoints lines =
+        let coordinates = Dictionary<int * int, int>()
+
+        let rec helper lines =
+            match lines with
+            | [||] -> coordinates
+            | _ ->
+                let { Start = x1, y1; End = x2, y2 } = lines.[0]
+
+                for x in (min x1 x2) .. (max x1 x2) do
+                    for y in (min y1 y2) .. (max y1 y2) do
+                        if coordinates.ContainsKey(x, y) then
+                            coordinates.[(x, y)] <- coordinates.[(x, y)] + 1
+                        else
+                            coordinates.[(x, y)] <- 1
+
+                helper (Array.tail lines)
+
+        helper lines |> ignore
+        coordinates.Values.Where(fun x -> x > 1).Count()
+
+    let day5 () =
+        InputFile
+        |> System.IO.File.ReadAllLines
+        |> Array.map parseLine
+        |> Array.filter isHorizontalOrVertical
+        |> countOverlapPoints