Add nix stuff

.clangd

@@ -0,0 +1,2 @@
+CompileFlags:
+	Add: [-std=c++20, -Wall]

.envrc

@@ -0,0 +1 @@
+use flake

.gitignore

@@ -4,3 +4,7 @@
 *data*.txt
 main
 main-[0-9]
+
+# Nix stuff
+result*
+/.direnv/

flake.lock

@@ -0,0 +1,26 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1701718080,
+        "narHash": "sha256-6ovz0pG76dE0P170pmmZex1wWcQoeiomUZGggfH9XPs=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "2c7f3c0fb7c08a0814627611d9d7d45ab6d75335",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "ref": "nixos-unstable",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  description = "It's Adventing Time";
+
+  inputs.nixpkgs.url = "nixpkgs/nixos-unstable";
+
+  outputs = {
+    self,
+    nixpkgs,
+  }: let
+    inherit (nixpkgs) lib;
+    genSystems = lib.genAttrs [
+      "x86_64-linux"
+      "aarch64-linux"
+    ];
+    pkgsFor = system: import nixpkgs {inherit system;};
+  in {
+    devShells = genSystems (
+      system: let
+        pkgs = pkgsFor system;
+      in {
+        default = pkgs.mkShell {
+          nativeBuildInputs = [
+            pkgs.clang-tools
+            (pkgs.sbcl.withPackages (p:
+              with p; [
+                alexandria
+                cl-ppcre
+                iterate
+                split-sequence
+                str
+              ]))
+            (pkgs.ghc.withPackages (p:
+              with p; [
+                containers
+                regex-compat
+                split
+                unordered-containers
+                vector
+              ]))
+          ];
+          CXXFLAGS = "-std=c++20 -Wall";
+        };
+      }
+    );
+
+    formatter = genSystems (system: (pkgsFor system).alejandra);
+  };
+}