Lean/2024/01: Add solution

Lean/2024/01.lean

@@ -0,0 +1,32 @@
+def Input := List Int × List Int
+
+def parse (input : String) : Input :=
+  input
+    |>.trim
+    |>.splitOn "\n"
+    |>.map (
+      fun line => line
+        |>.splitOn " "
+        |>.filter (not ∘ String.isEmpty)
+        |>.map String.toInt!
+        |> fun nums => (nums.head!, nums.getLast!)
+      )
+    |>.unzip
+
+def part1 (input : Input) : Nat :=
+  let fst := input.fst.mergeSort (· ≤ ·)
+  let snd := input.snd.mergeSort (· ≤ ·)
+  fst
+    |>.zip snd
+    |>.map (fun (a, b) => a - b |>.natAbs)
+    |>.foldl Nat.add 0
+
+def part2 (input : Input) : Int :=
+  input.fst
+    |>.map (fun a => a * (input.snd.count a))
+    |>.foldl Int.add 0
+
+def main (args : List String) : IO Unit := do
+  let input ← parse <$> (System.FilePath.mk args[0]! |> IO.FS.readFile)
+  IO.println $ part1 input
+  IO.println $ part2 input

Lean/justfile

@@ -0,0 +1,23 @@
+alias r := run
+alias e := example
+alias t := test
+alias ty := test-year
+alias ta := test-all
+
+_default:
+    @just --list
+
+run year day *args:
+    lean --run {{args}} {{year}}/{{day}}.lean ../.cache/{{year}}/{{trim_start_match(day, "0")}}
+
+example year day ex:
+    lean --run {{year}}/{{day}}.lean ../examples/{{year}}/{{trim_start_match(day, "0")}}/{{ex}}
+
+test year day:
+    @diff <(just run {{year}} {{day}}) <(cat ../.cache/{{year}}/{{trim_start_match(day, "0")}}.{1,2})
+
+test-year year:
+    @set -e; for day in $(ls {{year}}); do just test {{year}} $(basename $day .lean); done
+
+test-all:
+    @set -e; for year in *; do [[ -d $year ]] && [[ "$year" =~ ^[0-9]+$ ]] || continue; just test-year $year; done

flake.nix

@@ -159,6 +159,9 @@
           # Ruby
           ruby
           solargraph
+
+          # Lean
+          lean4
         ];
         PYTHONPATH = ".";
         LIBCLANG_PATH = with pkgs; lib.makeLibraryPath [llvmPackages.clang-unwrapped.lib];

scripts/generate-readme.py

@@ -14,6 +14,7 @@ names = {
     "nix": "Nix",
     "nu": "Nu",
     "rb": "Ruby",
+    "lean": "Lean",
 }
 exts = {
     "rs": [".rs"],
@@ -24,13 +25,14 @@ exts = {
     "nix": [".nix"],
     "nu": [".nu"],
     "rb": [".rb"],
+    "lean": [".lean"],
 }
 
 logos = {k.name.split(".")[0]: str(k) for k in Path(".assets").iterdir()}
 
 
 def logo(lang, height=12):
-    return f'<img height={height} src="{logos[lang]}">'
+    return f'<img height={height} src="{logos[lang]}">' if lang in logos else ""
 
 
 def link(year, day, lang):
@@ -51,7 +53,7 @@ def link(year, day, lang):
         else:
             url = f"{names[lang]}/{year}/{day:02}{ext}"
 
-        return f' [{logo(lang)}]({url} "{names[lang]} solution for {year}/{day:02}")'
+        return f' [{logo(lang) or names[lang]}]({url} "{names[lang]} solution for {year}/{day:02}")'
 
     return ""