My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add solution for 2023/22
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2023/day22.py
+114
2023/day22.py
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import fileinput
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import copy
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from itertools import permutations
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from utils import parse_nums
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def supports(b1, b2):
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# Returns true if b1 supports b2.
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ax, ay, az, bx, by, bz = b1
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cx, cy, cz, dx, dy, dz = b2
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b1_top = max(az, bz)
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b2_base = min(cz, dz)
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if b1_top + 1 != b2_base:
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return False
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ax, bx = min(ax, bx), max(ax, bx)
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ay, by = min(ay, by), max(ay, by)
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cx, dx = min(cx, dx), max(cx, dx)
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cy, dy = min(cy, dy), max(cy, dy)
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# can't support because off on one axis
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if bx < cx or ax > dx:
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return False
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if by < cy or ay > dy:
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return False
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return True
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def simulate(bricks):
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"""Returns the set of brick IDs that moved in the simulation."""
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all_touched = set()
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stationary = set()
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while True:
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moved = False
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for i, brick in enumerate(bricks):
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if i in stationary:
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continue
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# If the brick is on the ground, it can't fall more.
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if brick[2] == 1 or brick[5] == 1:
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stationary.add(i)
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continue
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# See if brick is supported by any other b2
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supported = False
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for j, b2 in enumerate(bricks):
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if i == j:
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continue
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if supports(b2, brick):
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# Can't fall because b2 supports brick,
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# but it might fall in a later tick.
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supported = True
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if j in stationary:
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# Nah, it won't.
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stationary.add(i)
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break
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if not supported:
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# Make the brick fall one tick.
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brick[2] -= 1
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brick[5] -= 1
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# Brick i has now moved in this simulation.
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all_touched.add(i)
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moved = True
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break
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if not moved:
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break
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return all_touched
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# Read problem input.
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BRICKS = []
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for line in fileinput.input():
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BRICKS.append(list(parse_nums(line.strip())))
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# Try to simulate bricks lower to the ground first.
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BRICKS.sort(key=lambda b: min(b[2], b[5]))
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simulate(BRICKS)
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# graph[a] -> b means a supports b.
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graph = {i: set() for i in range(len(BRICKS))}
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for i, j in permutations(range(len(BRICKS)), 2):
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if supports(BRICKS[i], BRICKS[j]):
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graph[i].add(j)
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part_1 = 0
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part_2 = 0
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for k in graph:
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# Nothing above this brick.
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if not graph[k]:
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part_1 += 1
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continue
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# Simulate removing the brick.
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without_brick = [copy.copy(BRICKS[i]) for i in range(len(BRICKS)) if i != k]
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num_moved = len(simulate(without_brick))
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if num_movedd == 0:
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part_1 += 1
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else:
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part_2 += num_moved
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print("Part 1:", part_1)
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print("Part 2:", part_2)