My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Update day12.py
+14
-17
+14
-17
2019/day12.py
+14
-17
2019/day12.py
···
1
1
import fileinput
2
-
from copy import deepcopy
3
2
from itertools import count
4
3
5
4
from utils import parse_nums
6
5
7
6
8
-
def gcd(a,b):
7
+
def gcd(a, b):
9
8
"""Compute the greatest common divisor of a and b"""
10
9
while b > 0:
11
10
a, b = b, a % b
12
11
return a
12
+
13
13
14
14
def lcm(a, b):
15
15
"""Compute the lowest common multiple of a and b"""
···
17
17
18
18
19
19
positions = []
20
+
initial = []
21
+
velocities = [[0] * 3 for _ in range(4)]
22
+
20
23
for i, line in enumerate(fileinput.input()):
21
24
line = line.strip()
22
25
nums = parse_nums(line)
23
26
positions.append(list(nums))
24
-
25
-
26
-
velocities = [[0] * 3 for _ in range(4)]
27
+
initial.append(list(nums))
27
28
28
-
INIT_POS = deepcopy(positions)
29
-
INIT_VEL = deepcopy(velocities)
30
29
CYCLES = [None, None, None]
31
30
32
-
for i in count(start=1):
31
+
for step in count(start=1):
33
32
# Update velocities
34
33
for x in range(4):
35
34
for y in range(x + 1, 4):
···
46
45
for d in range(3):
47
46
positions[x][d] += velocities[x][d]
48
47
49
-
energy = 0
48
+
if step == 1000:
49
+
energy = 0
50
50
51
-
for pos, vel in zip(positions, velocities):
52
-
pot = sum(abs(p) for p in pos)
53
-
kin = sum(abs(p) for p in vel)
54
-
energy += pot * kin
51
+
for pos, vel in zip(positions, velocities):
52
+
energy += sum(abs(p) for p in pos) * sum(abs(v) for v in vel)
55
53
56
-
if i == 1000:
57
54
print "Total energy after 1000 steps:", energy
58
55
59
56
for d in range(3):
···
61
58
continue
62
59
63
60
for m in range(4):
64
-
if positions[m][d] != INIT_POS[m][d]:
61
+
if positions[m][d] != initial[m][d]:
65
62
break
66
-
if velocities[m][d] != INIT_VEL[m][d]:
63
+
if velocities[m][d] != 0:
67
64
break
68
65
else:
69
-
CYCLES[d] = i
66
+
CYCLES[d] = step
70
67
71
68
if all(CYCLES):
72
69
print "Steps for full cycle:", lcm(lcm(CYCLES[0], CYCLES[1]), CYCLES[2])