Day 24: Never Tell Me The Odds (part 1)

README.md

@@ -28,4 +28,4 @@ Development occurs in language-specific directories:
 |[Day21.hs](hs/src/Day21.hs)|[Day21.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day21.kt)|[day21.py](py/aoc2023/day21.py)|[day21.rs](rs/src/day21.rs)|
 |[Day22.hs](hs/src/Day22.hs)|[Day22.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day22.kt)|[day22.py](py/aoc2023/day22.py)|[day22.rs](rs/src/day22.rs)|
 ||[Day23.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day23.kt)|||
-|[Day24.hs](hs/src/Day24.hs) ½||||
+|[Day24.hs](hs/src/Day24.hs) ½||[day24.py](py/aoc2023/day24.py) ½||

py/aoc2023/day24.py

@@ -0,0 +1,60 @@
+"""
+Day 24: Never Tell Me The Odds
+"""
+
+SAMPLE_INPUT = """19, 13, 30 @ -2,  1, -2
+18, 19, 22 @ -1, -1, -2
+20, 25, 34 @ -2, -2, -4
+12, 31, 28 @ -1, -2, -1
+20, 19, 15 @  1, -5, -3
+"""
+
+
+def _parse(data):
+    for line in data.splitlines():
+        if not line:
+            continue
+        pos, vel = line.split("@")
+        x, y, z = (int(num.strip()) for num in pos.split(","))
+        vx, vy, vz = (int(num.strip()) for num in vel.split(","))
+        yield (x, y, z), (vx, vy, vz)
+
+
+# pylint: disable=too-many-locals
+def part1(data, lo=200000000000000, hi=400000000000000):
+    """
+    >>> part1(SAMPLE_INPUT, lo=7, hi=27)
+    2
+    """
+    lines, acc = [], 0
+    for point in _parse(data):
+        (x0, y0, _), (vx0, vy0, _) = point
+        assert vx0
+        m0 = vy0 / vx0
+        b0 = y0 - x0 * vy0 / vx0
+        for m1, b1, x1, vx1 in lines:
+            if m0 == m1:
+                assert b0 != b1
+                continue
+            x = (b0 - b1) / (m1 - m0)
+            if (
+                lo <= x <= hi
+                and (x - x0) * vx0 > 0
+                and (x - x1) * vx1 > 0
+                and lo <= m0 * x + b0 <= hi
+            ):
+                acc += 1
+        lines.append((m0, b0, x0, vx0))
+    return acc
+
+
+def part2(data):
+    """
+    >>> part2(SAMPLE_INPUT) # doctest: +SKIP
+    47
+    """
+    _parse(data)
+    raise NotImplementedError()
+
+
+parts = (part1,)

py/pyproject.toml

@@ -44,6 +44,7 @@ day19 = "aoc2023.day19:parts"
 day20 = "aoc2023.day20:parts"
 day21 = "aoc2023.day21:parts"
 day22 = "aoc2023.day22:parts"
+day24 = "aoc2023.day24:parts"
 
 [tool.black]
 target_version = ["py312"]