From 3375d25b92492b99d8edf383b97ca881f6f7ab75 Mon Sep 17 00:00:00 2001
From: Nettika <nettika@leaf.ninja>
Date: Wed, 20 Dec 2023 20:58:01 -0800
Subject: [PATCH] Solve day 9

---
 advent_of_code/__init__.py |  3 ++-
 advent_of_code/oasis.py    | 28 +++++++++++++++++++++++
 tests/oasis_test.py        | 46 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 76 insertions(+), 1 deletion(-)
 create mode 100644 advent_of_code/oasis.py
 create mode 100644 tests/oasis_test.py

diff --git a/advent_of_code/__init__.py b/advent_of_code/__init__.py
index b630c26..dc3e813 100644
--- a/advent_of_code/__init__.py
+++ b/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),
 }
diff --git a/advent_of_code/oasis.py b/advent_of_code/oasis.py
new file mode 100644
index 0000000..b529987
--- /dev/null
+++ b/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)
diff --git a/tests/oasis_test.py b/tests/oasis_test.py
new file mode 100644
index 0000000..03b169a
--- /dev/null
+++ b/tests/oasis_test.py
@@ -0,0 +1,46 @@
+from advent_of_code.oasis import (
+    extrapolate_sequence,
+    parse_sequence,
+    solve_part_1,
+    solve_part_2,
+)
+
+
+def test_parse_sequencce():
+    assert parse_sequence("1 2 3") == (1, 2, 3)
+
+
+def test_extrapolate_sequence():
+    assert extrapolate_sequence((0, 3, 6, 9, 12, 15)) == 18
+    assert extrapolate_sequence((1, 3, 6, 10, 15, 21)) == 28
+    assert extrapolate_sequence((10, 13, 16, 21, 30, 45)) == 68
+
+
+def test_solve_part_1():
+    assert (
+        solve_part_1(
+            "\n".join(
+                [
+                    "0 3 6 9 12 15",
+                    "1 3 6 10 15 21",
+                    "10 13 16 21 30 45",
+                ]
+            )
+        )
+        == 114
+    )
+
+
+def test_solve_part_2():
+    assert (
+        solve_part_2(
+            "\n".join(
+                [
+                    "0 3 6 9 12 15",
+                    "1 3 6 10 15 21",
+                    "10 13 16 21 30 45",
+                ]
+            )
+        )
+        == 2
+    )