2025 day 1

adventofcode/2025/day1/day1.py

@@ -0,0 +1,43 @@
+def part1(lines):
+    pos = 50
+    cnt = 0
+    for rotation in lines:
+        direction = -1 if rotation[0] == "L" else 1
+        amount = int(rotation[1:])
+        pos = (pos + amount * direction) % 100
+        if pos == 0:
+            cnt += 1
+    print("Part 1: ", cnt)
+
+
+
+def part2(lines):
+    pos = 50
+    cnt = 0
+    for rotation in lines:
+        direction = -1 if rotation[0] == "L" else 1
+        amount = int(rotation[1:])
+        pos0 = pos % 100
+        # k0  is the smallest positive number of clicks (1..100) after the
+        # start of the current rotation at which the dial first reaches
+        # position 0.
+        k0 = ((100 - pos0) % 100) if direction == 1 else (pos0 % 100)
+        if k0 == 0:
+            k0 = 100
+        if amount >= k0:
+            cnt += 1 + (amount - k0) // 100
+        pos = (pos + direction * amount) % 100
+        print(rotation, pos, cnt)
+    print("Part 2: ", cnt)
+
+
+if __name__ == "__main__":
+    import sys
+    infile = sys.argv[1]
+    
+    with open(infile) as f:
+        lines = f.readlines()
+        lines = [x.rstrip() for x in lines]
+        part1(lines)
+        part2(lines)
+