1 files changed, 36 insertions, 0 deletions
diff --git a/day12.fsx b/day12.fsx
new file mode 100644
index 0000000..af458c2
--- /dev/null
+++ b/day12.fsx
@@ -0,0 +1,36 @@
+open System.IO
+open System.Text.RegularExpressions
+open System.Collections.Generic
+
+let getConnection line = 
+    let idRegex = new Regex("\d+")
+    let ids = idRegex.Matches(line)
+    match [for ID in ids -> ID.Value] with
+    | [] -> ("", [])
+    | head::tail -> (head, tail)
+
+let rec visit (connections: Dictionary<string, list<string>>) (visited: HashSet<string>) origin =
+    if not (visited.Add(origin)) then ()
+    else
+        for child in connections[origin] do visit connections visited child
+
+let checkInGroups (groups: seq<HashSet<string>>) (origin:string) =
+    Seq.fold (fun acc (group: HashSet<string>) -> acc || group.Contains(origin)) false groups
+
+let () = 
+    let pipes = new Dictionary<string, list<string>>()
+    File.ReadAllLines "day12.txt" |> Array.map getConnection |> Array.iter (fun (head, tail) -> pipes[head] <- tail)
+
+    let reachable = new HashSet<string>()
+    visit pipes reachable "0"
+    printfn "%A" reachable.Count
+    
+    let groups = new List<HashSet<string>>()
+    for origin in pipes.Keys do
+        if checkInGroups groups origin then ()
+        else
+            let newGroup = new HashSet<string>()
+            visit pipes newGroup origin
+            groups.Add(newGroup)
+        
+    printfn "%A" groups.Count