2024: d03: ex2: add solution

2024/d03/ex2/ex2.py

@@ -0,0 +1,42 @@
+#!/usr/bin/env python
+
+import dataclasses
+import re
+import sys
+
+
+@dataclasses.dataclass
+class MulInstruction:
+    lhs: int
+    rhs: int
+
+    def calc(self) -> int:
+        return self.lhs * self.rhs
+
+
+def solve(input: str) -> int:
+    def parse(input: str) -> list[MulInstruction]:
+        res: list[MulInstruction] = []
+
+        MUL_REGEX = re.compile(r"do\(\)|don't\(\)|mul\((\d+),(\d+)\)")
+        do = True
+        for match in MUL_REGEX.finditer(input):
+            if match.group(0) in ("do()", "don't()"):
+                do = match.group(0) == "do()"
+                continue
+            if not do:
+                continue
+            res.append(MulInstruction(int(match.group(1)), int(match.group(2))))
+
+        return res
+
+    return sum(inst.calc() for inst in parse(input))
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()