Day 9: Mirage Maintenance

README.md

@@ -13,4 +13,4 @@ Development occurs in language-specific directories:
 |[Day6.hs](hs/src/Day6.hs)|[Day6.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day6.kt)|[day6.py](py/aoc2023/day6.py)|[day6.rs](rs/src/day6.rs)|
 |[Day7.hs](hs/src/Day7.hs)|[Day7.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day7.kt)|[day7.py](py/aoc2023/day7.py)|[day7.rs](rs/src/day7.rs)|
 |[Day8.hs](hs/src/Day8.hs)|[Day8.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day8.kt)|[day8.py](py/aoc2023/day8.py)|[day8.rs](rs/src/day8.rs)|
-|[Day9.hs](hs/src/Day9.hs)|[Day9.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day9.kt)|||
+|[Day9.hs](hs/src/Day9.hs)|[Day9.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day9.kt)|[day9.py](py/aoc2023/day9.py)||

py/aoc2023/day9.py

@@ -0,0 +1,40 @@
+"""
+Day 9: Mirage Maintenance
+"""
+
+SAMPLE_INPUT = """
+0 3 6 9 12 15
+1 3 6 10 15 21
+10 13 16 21 30 45
+"""
+
+
+def _extrapolate(nums):
+    if any(nums):
+        return nums[-1] + _extrapolate([y - x for x, y in zip(nums, nums[1:])])
+    return 0
+
+
+def part1(data):
+    """
+    >>> part1(SAMPLE_INPUT)
+    114
+    """
+    return sum(
+        _extrapolate([int(word) for word in line.split() if word])
+        for line in data.splitlines()
+    )
+
+
+def part2(data):
+    """
+    >>> part2(SAMPLE_INPUT)
+    2
+    """
+    return sum(
+        _extrapolate([int(word) for word in line.split() if word][::-1])
+        for line in data.splitlines()
+    )
+
+
+parts = (part1, part2)

py/pyproject.toml

@@ -30,6 +30,7 @@ day5 = "aoc2023.day5:parts"
 day6 = "aoc2023.day6:parts"
 day7 = "aoc2023.day7:parts"
 day8 = "aoc2023.day8:parts"
+day9 = "aoc2023.day9:parts"
 
 [tool.black]
 target_version = ["py312"]