From 1dc59c18ebbf05ba1b1083db6f9d8f83fe259fd7 Mon Sep 17 00:00:00 2001
From: Bert Peters <bert@bertptrs.nl>
Date: Mon, 1 Dec 2025 08:59:13 +0100
Subject: [PATCH] Solve 2025 day 1 part 1

---
 2025/day01/sample.txt | 10 ++++++++++
 2025/day01/solve.nix  | 31 +++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)
 create mode 100644 2025/day01/sample.txt
 create mode 100644 2025/day01/solve.nix

diff --git a/2025/day01/sample.txt b/2025/day01/sample.txt
new file mode 100644
index 0000000..53287c7
--- /dev/null
+++ b/2025/day01/sample.txt
@@ -0,0 +1,10 @@
+L68
+L30
+R48
+L5
+R60
+L55
+L1
+L99
+R14
+L82
diff --git a/2025/day01/solve.nix b/2025/day01/solve.nix
new file mode 100644
index 0000000..2a4f4b3
--- /dev/null
+++ b/2025/day01/solve.nix
@@ -0,0 +1,31 @@
+{
+    solve = input_file:
+        let
+            data = builtins.readFile input_file;
+            lines = builtins.filter (s: s != "" && builtins.isString s) (builtins.split "\n" data);
+
+            mod = a: b: a - (a / b) * b;
+
+            recurse = list: position:
+                let
+                    first = builtins.head list;
+                    # This is not guaranteed to work but it does
+                    num_part = builtins.substring 1 999 first;
+                    num = builtins.fromJSON num_part;
+                    next = if (builtins.substring 0 1 first) == "R"
+                        then
+                            position + num
+                        else
+                            position - num;
+
+                    new_position = mod ((mod next 100) + 100) 100; 
+                    
+                    score = if new_position == 0 then 1 else 0;
+                in
+                    if list == [] then
+                        0
+                    else
+                        score + (recurse (builtins.tail list) new_position);
+        in
+            recurse lines 50;
+}