My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add solution for 2019/12
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2019/day12.py
+73
2019/day12.py
···
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import fileinput
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from copy import deepcopy
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from itertools import count
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from utils import parse_nums
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def gcd(a,b):
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"""Compute the greatest common divisor of a and b"""
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while b > 0:
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a, b = b, a % b
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return a
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def lcm(a, b):
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"""Compute the lowest common multiple of a and b"""
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return a * b / gcd(a, b)
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positions = []
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for i, line in enumerate(fileinput.input()):
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line = line.strip()
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nums = parse_nums(line)
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positions.append(list(nums))
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velocities = [[0] * 3 for _ in range(4)]
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INIT_POS = deepcopy(positions)
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INIT_VEL = deepcopy(velocities)
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CYCLES = [None, None, None]
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for i in count(start=1):
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# Update velocities
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for x in range(4):
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for y in range(x + 1, 4):
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for d in range(3):
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if positions[x][d] < positions[y][d]:
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velocities[x][d] += 1
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velocities[y][d] -= 1
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elif positions[x][d] > positions[y][d]:
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velocities[x][d] -= 1
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velocities[y][d] += 1
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# Update positions
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for x in range(4):
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for d in range(3):
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positions[x][d] += velocities[x][d]
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energy = 0
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for pos, vel in zip(positions, velocities):
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pot = sum(abs(p) for p in pos)
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kin = sum(abs(p) for p in vel)
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energy += pot * kin
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if i == 1000:
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print "Total energy after 1000 steps:", energy
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for d in range(3):
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if CYCLES[d] is not None:
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continue
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for m in range(4):
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if positions[m][d] != INIT_POS[m][d]:
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break
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if velocities[m][d] != INIT_VEL[m][d]:
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break
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else:
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CYCLES[d] = i
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if all(CYCLES):
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print "Steps for full cycle:", lcm(lcm(CYCLES[0], CYCLES[1]), CYCLES[2])
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break
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2019/inputs/12.txt
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2019/inputs/12.txt