Implement day 3 solver

puzzles/3.py

@@ -0,0 +1,35 @@
+import re
+from functools import reduce
+
+test_input_p1 = "xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))"
+test_input_p2 = "xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))"
+
+test_solution_p1 = 161
+test_solution_p2 = 48
+
+instruction_pattern = re.compile(r"mul\((\d+),(\d+)\)|(do(?:n't)?)\(\)")
+
+
+def solve_p1(puzzle_input: str) -> int:
+    instructions = (
+        tuple(map(int, match[:2]))
+        for match in instruction_pattern.findall(puzzle_input)
+        if match[0]
+    )
+    return sum(a * b for a, b in instructions)
+
+
+def solve_p2(puzzle_input: str) -> int:
+    instructions = (
+        match[2] or tuple(map(int, match[:2]))
+        for match in instruction_pattern.findall(puzzle_input)
+    )
+    return reduce(
+        lambda a, i: (
+            (1 if i == "do" else 0, a[1])
+            if isinstance(i, str)
+            else (a[0], a[1] + a[0] * i[0] * i[1])
+        ),
+        instructions,
+        (1, 0),
+    )[1]