2025: d01: ex2: add solution

2025/d01/ex1/ex1.py

@@ -0,0 +1,27 @@
+#!/usr/bin/env python
+
+import itertools
+import sys
+
+
+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]
+
+    turns = parse(input)
+    positions = itertools.accumulate(turns, initial=50)
+    return sum(pos % 100 == 0 for pos in positions)
+
+
+def main() -> None:
+    input = sys.stdin.read().splitlines()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()

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()