2023.24

challenges/2023/24-neverTellMeTheOdds/README.md

@@ -0,0 +1,7 @@
+# [Day 24: Never Tell Me The Odds](https://adventofcode.com/2023/day/24)
+
+Part 1 is not:
+* 1344 (too low)
+* 48384 (too high)
+
+Running this solution requires `z3-solver` to be installed.

challenges/2023/24-neverTellMeTheOdds/main.py

@@ -0,0 +1,112 @@
+import sys
+from collections import namedtuple
+from numbers import Number
+import gridutil.coord as cu
+from functools import reduce
+import math
+import z3
+
+
+Hailstone = namedtuple("Hailstone", ["position", "velocity"])
+
+
+def parse(instr: str) -> list[Hailstone]:
+    return [
+        Hailstone(
+            *map(lambda x: cu.Coordinate3(*map(int, x.split(", "))), line.split(" @ "))
+        )
+        for line in instr.splitlines()
+    ]
+
+
+def get_2d_line(stone: Hailstone) -> tuple[Number, Number]:
+    m = stone.velocity.y / stone.velocity.x
+    c = stone.position.y - (m * stone.position.x)
+    return m, c
+
+
+def get_2d_intersection(a: Hailstone, b: Hailstone) -> cu.Coordinate | None:
+    m1, c1 = get_2d_line(a)
+    m2, c2 = get_2d_line(b)
+
+    if math.isclose(m1, m2):
+        return None
+
+    x = (c2 - c1) / (m1 - m2)
+    y = (m1 * x) + c1
+    return cu.Coordinate(x, y)
+
+
+def one(instr: str):
+    hailstones = parse(instr)
+
+    MIN, MAX = (7, 27) if len(hailstones) == 5 else (200000000000000, 400000000000000)
+
+    acc = 0
+    for i, stone1 in enumerate(hailstones[:-1]):
+        for stone2 in hailstones[i + 1 :]:
+            if stone1 == stone2:
+                continue
+
+            p = get_2d_intersection(stone1, stone2)
+            if p is None or not reduce(lambda acc, x: acc and MIN <= x <= MAX, p, True):
+                continue
+
+            if not (
+                (p.x > stone1.position.x) == (stone1.velocity.x > 0)
+                and (p.x > stone2.position.x) == (stone2.velocity.x > 0)
+            ):
+                continue
+            acc += 1
+
+    return acc
+
+
+def two(instr: str):
+    hailstones = parse(instr)
+
+    # for our thrown rock
+    #     initial position: x,  y,  z
+    #     velocity:         vx, vy, vz
+
+    # for each of 3 hailstones
+    #     time of collision with that hailstone: t_i
+    #     intial position:                       hx,  hy,  hz
+    #     velocity:                              hvx, hvy, hvz
+
+    x, y, z = (z3.Int(x) for x in ["x", "y", "z"])
+    vx, vy, vz = (z3.Int(x) for x in ["vx", "vy", "vz"])
+
+    solver = z3.Solver()
+
+    for i in range(3):
+        hailstone = hailstones[i]
+        t = z3.Int(f"t_{i}")
+        solver.add(
+            t >= 0,
+            x + (vx * t) == hailstone.position.x + (hailstone.velocity.x * t),
+            y + (vy * t) == hailstone.position.y + (hailstone.velocity.y * t),
+            z + (vz * t) == hailstone.position.z + (hailstone.velocity.z * t),
+        )
+
+    _debug("Solving...", end="", flush=True)
+    assert solver.check() == z3.sat
+    model = solver.model()
+    _debug("\r            \r" + str(model))
+    return sum(model[var].as_long() for var in [x, y, z])
+
+
+def _debug(*args, **kwargs):
+    kwargs["file"] = sys.stderr
+    print(*args, **kwargs)
+
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2 or sys.argv[1] not in ["1", "2"]:
+        print("Missing day argument", file=sys.stderr)
+        sys.exit(1)
+    inp = sys.stdin.read().strip()
+    if sys.argv[1] == "1":
+        print(one(inp))
+    else:
+        print(two(inp))

challenges/2023/24-neverTellMeTheOdds/tests.json

@@ -0,0 +1,14 @@
+{
+    "1": [
+        {
+            "is": "2",
+            "input": "19, 13, 30 @ -2,  1, -2\n18, 19, 22 @ -1, -1, -2\n20, 25, 34 @ -2, -2, -4\n12, 31, 28 @ -1, -2, -1\n20, 19, 15 @  1, -5, -3\n\n"
+        }
+    ],
+    "2": [
+        {
+            "is": "47",
+            "input": "19, 13, 30 @ -2,  1, -2\n18, 19, 22 @ -1, -1, -2\n20, 25, 34 @ -2, -2, -4\n12, 31, 28 @ -1, -2, -1\n20, 19, 15 @  1, -5, -3\n\n"
+        }
+    ]
+}

challenges/2023/README.md

@@ -35,3 +35,4 @@ A day denoted with a star means it has a visualisation.
 | 21 - Step Counter | ★ ☆ | Python | ??? |
 | 22 - Sand Slabs | ★ ★ | Python | I maintain that OpenSCAD is the best AoC 3D debugging tool |
 | 23 - A Long Walk | ★ ★ | Python | Both parts here could theorietcially be done with the same implementation but I couldn't be bothered to rework the part 2 solution to work for part 1 as well. |
+| 24 - Never Tell Me The Odds | ★ ★ | Python | Z3 seems like an *incredible* useful tool but also not a satisfying puzzle at all :( |

challenges/2023/benchmarks.jsonl

@@ -41,3 +41,5 @@
 {"day": 22, "part": 2, "runner": "py", "min": 30.386138439178467, "max": 30.386138439178467, "avg": 30.386138439178467, "n": 1}
 {"day": 23, "part": 1, "runner": "py", "min": 2.006169557571411, "max": 2.006169557571411, "avg": 2.006169557571411, "n": 1}
 {"day": 23, "part": 2, "runner": "py", "min": 33.72923398017883, "max": 33.72923398017883, "avg": 33.72923398017883, "n": 1}
+{"day": 24, "part": 1, "runner": "py", "min": 0.12593984603881836, "max": 0.1335890293121338, "avg": 0.13133821487426758, "n": 5}
+{"day": 24, "part": 2, "runner": "py", "min": 4.988582134246826, "max": 6.0756916999816895, "avg": 5.414014768600464, "n": 5}