My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add solution for 2019/20
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2019/day20.py
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2019/day20.py
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import fileinput
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from string import ascii_uppercase
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from collections import defaultdict
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from utils import Point, DIRS
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MAZE = defaultdict(lambda: '#')
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PORTALS = defaultdict(set)
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PORTAL_MAP = {}
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AA = None
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ZZ = None
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INNERS = set()
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OUTERS = set()
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MAX_X = 0
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MAX_Y = 0
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# Read problem input
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for y, line in enumerate(fileinput.input()):
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for x, c in enumerate(line[:-1]):
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MAZE[Point(x, y)] = c
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MAX_X = max(MAX_X, x)
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MAX_Y = max(MAX_Y, y)
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# Determine the true label name and grid position of portals
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for p, c in MAZE.items():
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if c in ascii_uppercase:
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name = ''
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if MAZE[p + Point(-1, 0)] in ascii_uppercase:
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name = MAZE[p + Point(-1, 0)] + c
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op = p + Point(-1, 0)
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elif MAZE[p + Point(1, 0)] in ascii_uppercase:
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name = c + MAZE[p + Point(1, 0)]
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op = p + Point(1, 0)
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elif MAZE[p + Point(0, -1)] in ascii_uppercase:
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name = MAZE[p + Point(0, -1)] + c
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op = p + Point(0, -1)
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elif MAZE[p + Point(0, 1)] in ascii_uppercase:
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name = c + MAZE[p + Point(0, 1)]
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op = p + Point(0, 1)
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for np in p.neighbours_4():
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if MAZE[np] == '.':
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portal_loc = np
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for np in op.neighbours_4():
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if MAZE[np] == '.':
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portal_loc = np
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if name == 'AA':
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AA = portal_loc
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elif name == 'ZZ':
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ZZ = portal_loc
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else:
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PORTALS[name].add(portal_loc)
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# Map portal positions and track inner/outer edges
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for x in PORTALS:
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a, b = list(PORTALS[x])
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PORTAL_MAP[a] = b
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PORTAL_MAP[b] = a
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if a.x == 2 or a.x == (MAX_X - 2) or a.y == 2 or a.y == (MAX_Y - 2):
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OUTERS.add(a)
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INNERS.add(b)
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else:
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OUTERS.add(b)
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INNERS.add(a)
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def bfs(start, end, recursive=False):
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horizon = [(start, 0)]
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seen = set()
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steps = 1
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while horizon:
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new_horizon = []
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for p, level in horizon:
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neighbours = p.neighbours_4()
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if p in PORTAL_MAP:
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if not (p in OUTERS and level == 0) or not recursive:
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neighbours.append(PORTAL_MAP[p])
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for np in neighbours:
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new_level = level
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if recursive:
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if p in INNERS and np in OUTERS:
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new_level += 1
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elif p in OUTERS and np in INNERS and level > 0:
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new_level -= 1
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if (np, new_level) in seen:
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continue
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if MAZE[np] != '.':
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continue
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if np == end and new_level == 0:
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return steps
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seen.add((np, new_level))
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new_horizon.append((np, new_level))
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horizon = new_horizon
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steps += 1
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print "Steps in basic maze:", bfs(AA, ZZ)
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print "Steps in recursive maze:", bfs(AA, ZZ, recursive=True)