Finish day 21

2 files changed, 71 insertions, 41 deletions

diff --git a/aoc-2022-dotnet/Day21/Program.fs b/aoc-2022-dotnet/Day21/Program.fs
index 3837054..f9a608d 100644
--- a/aoc-2022-dotnet/Day21/Program.fs
+++ b/aoc-2022-dotnet/Day21/Program.fs
@@ -1,61 +1,91 @@
 module Day21
 
 open System.IO
+open System.Numerics
 open FSharpPlus
 open FParsec
 open Common
 
 type MonkeyName = string
-type Operator = int64 -> int64 -> int64
+
+module MonkeyName =
+    let root = "root"
+    let human = "humn"
+
+type Operator = Complex -> Complex -> Complex
+
+module Operator =
+    let fromChar =
+        function
+        | '+' -> (+)
+        | '-' -> (-)
+        | '*' -> (*)
+        | '/' -> (/)
+        | c -> failwithf "Invalid operator: %c" c
+
+    let unknownExtractor l r =
+        let eq: Complex = l - r
+        Complex(round <| -eq.Real / eq.Imaginary, 0)
 
 type MonkeyJob =
-    | Number of int64
+    | Number of Complex
     | Operation of MonkeyName * Operator * MonkeyName
 
+    static member unknownVariable = Number(Complex(0, 1))
+
+    static member eval(cache: Map<MonkeyName, Complex>) =
+        function
+        | Number num -> num
+        | Operation (left, operator, right) -> operator cache[left] cache[right]
+
+    static member withOperator op =
+        function
+        | Operation (l, _, r) -> Operation(l, op, r)
+        | other -> other
+
     static member dependencies =
         function
-        | Number _ -> []
         | Operation (l, _, r) -> [ l; r ]
+        | _ -> []
 
 type Monkey = MonkeyName * MonkeyJob
 
-let charToOperator =
-    function
-    | '+' -> (+)
-    | '-' -> (-)
-    | '*' -> (*)
-    | '/' -> (/)
-    | c -> failwithf "Invalid operator: %c" c
-
-let parseMonkey =
-    let pspc = pchar ' '
-    let pname = anyString 4 |>> MonkeyName
-    let poper = pspc >>. anyChar .>> pspc |>> charToOperator
-    let pnumber = pint64 |>> Number
-    let poperation = tuple3 pname poper pname |>> Operation
-    let pjob = pnumber <|> poperation
-    let pmonkey = pname .>> pstring ": " .>>. pjob |>> Monkey
-    Util.parse pmonkey
-
-let solution input =
-    let monkeys = input |> Seq.map parseMonkey |> Map.ofSeq
-
-    monkeys
-    |> Map.mapValues MonkeyJob.dependencies
-    |> Util.tsort
-    |> List.fold
-        (fun values name ->
-            Map.add
-                name
-                (match monkeys[name] with
-                 | Number num -> num
-                 | Operation (left, operator, right) -> operator values[left] values[right])
-                values)
-        Map.empty
-    |> Map.find "root"
+module Monkey =
+    let parse =
+        let pws = pchar ' '
+        let pname = anyString 4 |>> MonkeyName
+        let pop = pws >>. anyChar .>> pws |>> Operator.fromChar
+        let pnumber = pfloat |>> (fun n -> Number(Complex(n, 0)))
+        let poperation = tuple3 pname pop pname |>> Operation
+        let pjob = pnumber <|> poperation
+        let pmonkey = pname .>> pstring ": " .>>. pjob |>> Monkey
+        Util.parse pmonkey
+
+let solution modification input =
+    let monkeys =
+        input
+        |> Seq.map Monkey.parse
+        |> Map.ofSeq
+        |> modification
+
+    let nodeValues =
+        monkeys
+        |> Map.mapValues MonkeyJob.dependencies
+        |> Util.tsort
+        |> List.fold (fun cache name -> Map.add name (MonkeyJob.eval cache monkeys[name]) cache) Map.empty
+
+    int64 nodeValues[MonkeyName.root].Real
+
+let part1 = id
+
+let part2 =
+    Map.add MonkeyName.human MonkeyJob.unknownVariable
+    >> Map.change MonkeyName.root (Option.map (MonkeyJob.withOperator Operator.unknownExtractor))
 
 let test = File.ReadLines("test.txt")
-assert (solution test = 152)
+assert (solution part1 test = 152)
+assert (solution part2 test = 301)
 
 let input = File.ReadLines("input.txt")
-printfn "%d" <| solution input
+printfn "%d" <| solution part1 input
+printfn "%d" <| solution part2 input
diff --git a/aoc-2022-dotnet/README.md b/aoc-2022-dotnet/README.md
index bc6029a..37de967 100644
--- a/aoc-2022-dotnet/README.md
+++ b/aoc-2022-dotnet/README.md
@@ -1,6 +1,6 @@
 # Advent of Code 2022 in F#
 ![F#](https://img.shields.io/badge/F%23-grey?logo=.NET)
-![Stars](https://img.shields.io/badge/🌟%20stars-38/50-orange)
+![Stars](https://img.shields.io/badge/🌟%20stars-40/50-orange)
 
 |  Day   | Problem Name                                                     | Part 1 | Part 2 | Practiced Concepts                                   |
 | :----: | ---------------------------------------------------------------- | :----: | :----: | ---------------------------------------------------- |
@@ -24,7 +24,7 @@
 | **18** | [Boiling Boulders](https://adventofcode.com/2022/day/18)         | :star: | :star: | functional DFS, 3D vectors, position bound checking  |
 | **19** | [Not Enough Minerals](https://adventofcode.com/2022/day/19)      |        |        |                                                      |
 | **20** | [Grove Positioning System](https://adventofcode.com/2022/day/20) | :star: | :star: | linked lists, modulo & remainder                     |
-| **21** | [Monkey Math](https://adventofcode.com/2022/day/21)              |        |        |                                                      |
+| **21** | [Monkey Math](https://adventofcode.com/2022/day/21)              | :star: | :star: | topological sort, ADTs, complex numbers              |
 | **22** | [Monkey Map](https://adventofcode.com/2022/day/22)               |        |        |                                                      |
 | **23** | [Unstable Diffusion](https://adventofcode.com/2022/day/23)       |        |        |                                                      |
 | **24** | [Blizzard Basin](https://adventofcode.com/2022/day/24)           |        |        |                                                      |