Solve day 9

advent_of_code/__init__.py

@@ -5,7 +5,7 @@ __version__ = "1.0.0"
 
 from typing import Callable
 
-from advent_of_code import cubes, gears, network, scratchcards, trebuchet
+from advent_of_code import cubes, gears, network, oasis, scratchcards, trebuchet
 
 Solver = Callable[[str], int]
 
@@ -16,4 +16,5 @@ solvers: dict[int, tuple[Solver, Solver]] = {
     3: (gears.solve_part_1, gears.solve_part_2),
     4: (scratchcards.solve_part_1, scratchcards.solve_part_2),
     8: (network.solve_part_1, network.solve_part_2),
+    9: (oasis.solve_part_1, oasis.solve_part_2),
 }

advent_of_code/oasis.py

@@ -0,0 +1,28 @@
+"Day 9: Mirage Maintenance"
+
+Sequence = tuple[int, ...]
+
+
+def parse_sequence(desc: str) -> Sequence:
+    return tuple(int(num) for num in desc.split(" "))
+
+
+def extrapolate_sequence(sequence: tuple[int, ...]) -> int:
+    if any(sequence):
+        difference_sequence = tuple(
+            right - left for left, right in zip(sequence, sequence[1:])
+        )
+        next_difference = extrapolate_sequence(difference_sequence)
+        return sequence[-1] + next_difference
+    return 0
+
+
+def solve_part_1(input: str) -> int:
+    sequences = (parse_sequence(desc) for desc in input.split("\n"))
+    return sum(extrapolate_sequence(sequence) for sequence in sequences)
+
+
+def solve_part_2(input: str) -> int:
+    sequences = (parse_sequence(desc) for desc in input.split("\n"))
+    reversed_sequences = (tuple(reversed(sequence)) for sequence in sequences)
+    return sum(extrapolate_sequence(sequence) for sequence in reversed_sequences)