My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add solution for 2019/18
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2019/day18.py
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2019/day18.py
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import fileinput
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from string import ascii_uppercase, ascii_lowercase
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from collections import defaultdict, deque
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from heapq import heappush, heappop
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from utils import Point
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BOARD = defaultdict(lambda: '#')
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KEYS = {}
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DOORS = {}
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ent = None
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for i, line in enumerate(fileinput.input()):
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for x, c in enumerate(line.strip()):
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BOARD[Point(x, i)] = c
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if c == '@':
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ent = Point(x, i)
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if c in ascii_lowercase:
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KEYS[c] = Point(x, i)
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if c in ascii_uppercase:
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DOORS[c] = Point(x, i)
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NUM_KEYS = len(KEYS)
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def part_1(start):
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horizon = [(start, frozenset())]
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seen = set()
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level = 0
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while horizon:
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new_horizon = []
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for p, k in horizon:
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for np in p.neighbours_4():
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if (np, k) in seen:
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continue
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if BOARD[np] != '#':
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c = BOARD[np]
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if c in DOORS and c.lower() not in k:
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continue
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if c in KEYS:
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if c in k:
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state = (np, k)
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else:
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state = (np, k | set([c]))
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# print state
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if len(state[1]) == NUM_KEYS:
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return level + 1
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new_horizon.append(state)
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seen.add(state)
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else:
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new_horizon.append((np, k))
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seen.add((np, k))
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# print "yes"
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horizon = new_horizon
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level += 1
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print "Minimal steps for Part 1:", part_1(ent)
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# Manual maze replacement for Part 2
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ents = []
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for np in ent.neighbours_8():
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if np.dist_manhattan(ent) == 2:
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ents.append(np)
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BOARD[np] = '@'
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else:
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BOARD[np] = '#'
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BOARD[ent] = '#'
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points = KEYS
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for i, ent in enumerate(ents):
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points[str(i)] = ent
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# print points
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# Preprocess graph to determine distances from each key to each other key
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# Edges are represented as start_pos: (steps, new_key, doors_passed).
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graph = defaultdict(list)
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for i, node in enumerate(points):
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# BFS from start pos to each key in quadrant
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# state is (pos, doors_passed)
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level = 1
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horizon = [(points[node], frozenset())]
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seen = set()
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while horizon:
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new_horizon = []
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for pos, doors in horizon:
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for np in pos.neighbours_4():
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if (np, doors) in seen:
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continue
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if BOARD[np] == '#':
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continue
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tile = BOARD[np]
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ndoors = doors
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if tile in ascii_uppercase:
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ndoors |= set([tile.lower()])
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if tile in ascii_lowercase and tile != node:
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graph[node].append((level, tile, ndoors))
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seen.add((np, ndoors))
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continue
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new_horizon.append((np, ndoors))
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seen.add((np, ndoors))
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horizon = new_horizon
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level += 1
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heap = [(0, '0', '1', '2', '3', frozenset())]
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seen = set()
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while heap:
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steps, a, b, c, d, keys = heappop(heap)
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if len(keys) == NUM_KEYS:
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print "Minimal steps for Part 2:", steps
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break
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for i, p in enumerate((a, b, c, d), start=1):
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for ns, np, nd in graph[p]:
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if not keys.issuperset(nd):
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continue
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next_state = [steps + ns, a, b, c, d, keys | set([np])]
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next_state[i] = np
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next_state = tuple(next_state)
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if next_state[1:] in seen:
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continue
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seen.add(next_state[1:])
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heappush(heap, next_state)