From 0863c640f7cb22d801bd39f73fdbafc7f5bdc3fa Mon Sep 17 00:00:00 2001
From: Bruno BELANYI <bruno@belanyi.fr>
Date: Mon, 1 Dec 2025 21:08:30 +0000
Subject: [PATCH] 2025: d01: ex2: add solution

---
 2025/d01/ex2/ex2.py | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100755 2025/d01/ex2/ex2.py

diff --git a/2025/d01/ex2/ex2.py b/2025/d01/ex2/ex2.py
new file mode 100755
index 0000000..d47c5cd
--- /dev/null
+++ b/2025/d01/ex2/ex2.py
@@ -0,0 +1,40 @@
+#!/usr/bin/env python
+
+import itertools
+import sys
+
+
+def sign(n: int) -> int:
+    if n == 0:
+        return 0
+    return n // abs(n)
+
+
+def solve(input: list[str]) -> int:
+    def parse_turn(input: str) -> int:
+        direction = input[0]
+        clicks = int(input[1:])
+        return clicks * (1 if direction == "R" else -1)
+
+    def parse(input: list[str]) -> list[int]:
+        return [parse_turn(turn) for turn in input]
+
+    def count_zeros(before: int, after: int) -> int:
+        delta = after - before
+        to_zero = (before % 100) * -sign(delta)
+        if to_zero <= 0:
+            to_zero += 100
+        return (abs(delta) + 100 - to_zero) // 100
+
+    turns = parse(input)
+    positions = itertools.accumulate(turns, initial=50)
+    return sum(count_zeros(a, b) for a, b in itertools.pairwise(positions))
+
+
+def main() -> None:
+    input = sys.stdin.read().splitlines()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()