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Faster 2023 day 24 (part 1).

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Mikaël Capelle 2024-01-01 18:44:13 +01:00
parent 3a9c7e728b
commit 7d2eb6b5ec
1 changed files with 20 additions and 25 deletions
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45
src/holt59/aoc/2023/day24.py
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@ -5,37 +5,32 @@ from sympy import solve, symbols
lines = sys.stdin.read().splitlines() lines = sys.stdin.read().splitlines()
positions = [ positions = np.array(
np.array([int(c) for c in line.split("@")[0].strip().split(", ")]) for line in lines [[int(c) for c in line.split("@")[0].strip().split(", ")] for line in lines]
] )
velocities = [ velocities = np.array(
np.array([int(c) for c in line.split("@")[1].strip().split(", ")]) for line in lines [[int(c) for c in line.split("@")[1].strip().split(", ")] for line in lines]
] )
# part 1 # part 1
low, high = [7, 27] if len(positions) <= 10 else [200000000000000, 400000000000000] low, high = [7, 27] if len(positions) <= 10 else [200000000000000, 400000000000000]
count = 0 count = 0
for i, (p1, v1) in enumerate(zip(positions, velocities)): for i1, (p1, v1) in enumerate(zip(positions, velocities)):
for p2, v2 in zip(positions[i + 1 :], velocities[i + 1 :]): p, r = p1[:2], v1[:2]
p, r = p1[:2], v1[:2]
q, s = p2[:2], v2[:2]
rs = np.cross(r, s) q, s = positions[i1 + 1 :, :2], velocities[i1 + 1 :, :2]
qpr = np.cross((q - p), r)
if rs == 0: rs = np.cross(r, s)
# assume there are no colinear lines
continue
else:
assert rs != 0
t = np.cross((q - p), s) / rs
u = np.cross((q - p), r) / rs
if t >= 0 and u >= 0: q, s, rs = q[m := (rs != 0)], s[m], rs[m]
c = p + t * r t = np.cross((q - p), s) / rs
u = np.cross((q - p), r) / rs
t, u = t[m := ((t >= 0) & (u >= 0))], u[m]
c = p + np.expand_dims(t, 1) * r
count += np.all((low <= c) & (c <= high), axis=1).sum()
if low <= c[0] <= high and low <= c[1] <= high:
count += 1
answer_1 = count answer_1 = count
print(f"answer 1 is {answer_1}") print(f"answer 1 is {answer_1}")
@ -58,8 +53,8 @@ x, y, z, vx, vy, vz, *ts = symbols(
"x y z vx vy vz " + " ".join(f"t{i}" for i in range(n + 1)) "x y z vx vy vz " + " ".join(f"t{i}" for i in range(n + 1))
) )
equations = [] equations = []
for i, ti in zip(range(n), ts): for i1, ti in zip(range(n), ts):
for p, d, pi, di in zip((x, y, z), (vx, vy, vz), positions[i], velocities[i]): for p, d, pi, di in zip((x, y, z), (vx, vy, vz), positions[i1], velocities[i1]):
equations.append(p + ti * d - pi - ti * di) equations.append(p + ti * d - pi - ti * di)
r = solve(equations, [x, y, z, vx, vy, vz] + list(ts), dict=True)[0] r = solve(equations, [x, y, z, vx, vy, vz] + list(ts), dict=True)[0]