Impl d1p1 in nix

day1/part1.nix

@@ -0,0 +1,41 @@
+let
+    # Import nixpkgs lib and input file
+    inherit ((builtins.getFlake (builtins.toString ./..)).inputs.nixpkgs) lib;
+    input = builtins.readFile (builtins.toString ./input.txt);
+
+    # Define functions
+    abs = n: if n < 0 then (-n) else n;
+
+    # Do parsing
+    parsed = ( # Define function to sort lines into two lists
+        lib.lists.foldr
+            (cur: acc: {
+                first = acc.first ++ [(lib.strings.toIntBase10 (builtins.elemAt cur 0))];
+                second = acc.second ++ [(lib.strings.toIntBase10 (builtins.elemAt cur 1))];
+            })
+            { first = []; second = []; }
+    ) ( # Call with input split on newlines and 3 spaces; formatted like [ [ 1 2 ] [ 3 4 ] [ 5 6 ] ]
+        lib.lists.forEach
+            (lib.strings.splitString "\n" input)
+            (e: lib.strings.splitString "   " e)
+    );
+    sorted = {
+        first = lib.lists.sort (a: b: a < b) parsed.first;
+        second = lib.lists.sort (a: b: a < b) parsed.second;
+    };
+    reorganized = (
+        lib.lists.imap0
+            (i: e: [ e (builtins.elemAt sorted.second i) ])
+            sorted.first
+    );
+
+    output = (
+        (
+            lib.lists.foldr
+                (cur: acc:
+                    acc + (abs ((builtins.elemAt cur 0) - (builtins.elemAt cur 1)))
+                )
+                0
+        ) reorganized
+    );
+in output

flake.lock

@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1733015953,
+        "lastModified": 1733759999,
-        "narHash": "sha256-t4BBVpwG9B4hLgc6GUBuj3cjU7lP/PJfpTHuSqE+crk=",
+        "narHash": "sha256-463SNPWmz46iLzJKRzO3Q2b0Aurff3U1n0nYItxq7jU=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "ac35b104800bff9028425fec3b6e8a41de2bbfff",
+        "rev": "a73246e2eef4c6ed172979932bc80e1404ba2d56",
         "type": "github"
       },
       "original": {