solution for day 3

2 files changed, 28 insertions, 0 deletions

diff --git a/Program.fs b/Program.fs
index e85d15f..7e7cb55 100644
--- a/Program.fs
+++ b/Program.fs
@@ -12,5 +12,7 @@ match (day, part) with
 | (1, 2) -> Day1.part2 () |> printf "%A\n"
 | (2, 1) -> Day2.part1 () |> printf "%A\n"
 | (2, 2) -> Day2.part2 () |> printf "%A\n"
+| (3, 1) -> Day3.part1 () |> printf "%A\n"
+| (3, 2) -> Day3.part2 () |> printf "%A\n"
 | (x, y) when (1 <= x && x <= 25) && (y = 1 || y = 2)  -> raise (NotImplemented("not implemented yet"))
 | _ -> raise (NotImplemented("invalid values"))
\ No newline at end of file
diff --git a/solutions/day3.fs b/solutions/day3.fs
new file mode 100644
index 0000000..cebfde5
--- /dev/null
+++ b/solutions/day3.fs
@@ -0,0 +1,26 @@
+namespace Solutions
+
+module Day3 =
+    open System.IO
+    
+    let lines = File.ReadLines("inputs/day3.txt")
+    let rucksacks = lines 
+                    |> Seq.map (fun x -> (Set.ofSeq x[0..x.Length / 2 - 1], Set.ofSeq x[x.Length/2..x.Length]))
+    let groups = lines 
+                    |> Seq.map Set.ofSeq 
+                    |> Seq.splitInto (Seq.length lines / 3)
+    
+    let prioritize ch =
+        match ch with
+        | x when 'a' <= x && x <= 'z' -> int x - int 'a' + 1
+        | x when 'A' <= x && x <= 'Z' -> int x - int 'A' + 27
+        | _ -> 0
+    
+    // extract the single element from the set with maxElement
+    let part1 () = rucksacks 
+                    |> Seq.map ((fun (x, y) -> Set.intersect x y |> Set.maxElement) >> prioritize)
+                    |> Seq.sum
+    
+    let part2 () = groups
+                    |> Seq.map (Set.intersectMany >> Set.maxElement >> prioritize)
+                    |> Seq.sum
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