day 1

2025/01/solution.py

@@ -0,0 +1,81 @@
+#!/usr/bin/env python3
+import sys
+import pathlib
+
+def read_input():
+    path = pathlib.Path(sys.argv[1]) if len(sys.argv) > 1 else pathlib.Path("input.txt")
+    return path.read_text().rstrip("\n")
+
+def parse(data):
+    return data.splitlines()
+
+def part1(data):
+    password = 0
+    postion = 50
+
+    for rotation in data:
+        direction = rotation[0]
+        dist = int(rotation[1:])
+
+        if direction == "R":
+            postion += dist
+        else: # left case
+            postion -= dist
+        postion %= 100
+        if postion == 0:
+            password += 1
+
+    return password
+
+def part2(data):
+    password = 0
+    pos = 50
+    modulo = 100
+
+    for rotation in data:
+        direction = rotation[0]
+        num = int(rotation[1:])
+        old_pos = pos
+
+        if direction == 'L':
+            pos -= num
+        else:
+            pos += num
+
+        if old_pos != pos:
+            old = old_pos
+            new = pos
+            if old < new:
+                first = (old // modulo + 1) * modulo
+                last = (new // modulo) * modulo
+                if first <= new:
+                    crosses = (last - first) // modulo + 1
+                else:
+                    crosses = 0
+            else:
+                if new % modulo == 0:
+                    first = new
+                else:
+                    first = (new // modulo + 1) * modulo
+                last = ((old - 1) // modulo) * modulo
+                if first <= last:
+                    crosses = (last - first) // modulo + 1
+                else:
+                    crosses = 0
+        else:
+            crosses = 0
+
+        password += crosses
+
+    return password
+
+def main():
+    raw = read_input()
+    data = parse(raw)
+    r1 = part1(data)
+    r2 = part2(data)
+    print(r1)
+    print(r2)
+
+if __name__ == "__main__":
+    main()