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day23.py
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day23.py
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import unittest
import heapq
SLOPE = {
'>': (1, 0),
'<': (-1, 0),
'^': (0, -1),
'v': (0, 1)
}
DIR = SLOPE.values()
def parseInput(input):
return [line for line in input.splitlines()]
def add(a, b):
return (a[0] + b[0], a[1] + b[1])
def maxPath(data, start, goal, slope):
paths = [(0, [start])]
best = 0
while len(paths):
steps, path = heapq.heappop(paths)
pos = path[-1]
if pos == goal:
best = max(best, -steps)
continue
for dir in DIR:
next = add(pos, dir)
x, y = next
if x < 0 or x >= len(data[0]) or y < 0 or y >= len(data): continue
c = data[y][x]
if c == '#': continue
if next in path: continue
npath = path.copy()
if c in slope:
nn = add(next, slope[c])
if nn == pos: continue
npath.append(nn)
heapq.heappush(paths, (steps - 2, npath))
else:
npath.append(next)
heapq.heappush(paths, (steps - 1, npath))
return best
def maxPath2(data, start, goal):
visited = set()
nodes = [(start, 0, start)]
graph = {
start: []
}
while len(nodes):
parent, dist, pos = nodes.pop()
def valid(dir):
next = add(pos, dir)
x, y = next
if x < 0 or x >= len(data[0]) or y < 0 or y >= len(data): return False
c = data[y][x]
if c == '#': return False
return True
neighbours = [dir for dir in DIR if valid(dir)]
if len(neighbours) < 3:
if pos in visited: continue
visited.add(pos)
if pos == goal:
graph[goal] = [(parent, dist)]
graph[parent].append((goal, dist))
continue
if len(neighbours) == 1 and pos != start:
# Skip dead ends
continue
if len(neighbours) == 2 or pos == start:
for dir in neighbours:
next = add(pos, dir)
if not next in visited and parent != next:
nodes.append((parent, dist + 1, next))
continue
if not pos in graph: graph[pos] = []
graph[pos].append((parent, dist))
graph[parent].append((pos, dist))
for dir in neighbours:
next = add(pos, dir)
nodes.append((pos, 1, next))
paths = [(0, [start])]
result = 0
while len(paths):
dist, path = paths.pop()
current = path[-1]
if current == goal:
result = max(result, dist)
continue
for next, w in graph[current]:
if next in path: continue
next_path = path.copy()
next_path.append(next)
paths.append((w + dist, next_path))
return result
def parse1(input):
data = parseInput(input)
return maxPath(data, (1, 0), (len(data[0]) - 2, len(data) - 1), SLOPE)
def parse2(input):
data = parseInput(input)
return maxPath2(data, (1, 0), (len(data[0]) - 2, len(data) - 1))
class Test(unittest.TestCase):
def test_part1(self):
self.assertEqual(parse1("""#.#####################
#.......#########...###
#######.#########.#.###
###.....#.>.>.###.#.###
###v#####.#v#.###.#.###
###.>...#.#.#.....#...#
###v###.#.#.#########.#
###...#.#.#.......#...#
#####.#.#.#######.#.###
#.....#.#.#.......#...#
#.#####.#.#.#########v#
#.#...#...#...###...>.#
#.#.#v#######v###.###v#
#...#.>.#...>.>.#.###.#
#####v#.#.###v#.#.###.#
#.....#...#...#.#.#...#
#.#########.###.#.#.###
#...###...#...#...#.###
###.###.#.###v#####v###
#...#...#.#.>.>.#.>.###
#.###.###.#.###.#.#v###
#.....###...###...#...#
#####################.#"""), 94)
def test_part2(self):
self.assertEqual(parse2("""#.#####################
#.......#########...###
#######.#########.#.###
###.....#.>.>.###.#.###
###v#####.#v#.###.#.###
###.>...#.#.#.....#...#
###v###.#.#.#########.#
###...#.#.#.......#...#
#####.#.#.#######.#.###
#.....#.#.#.......#...#
#.#####.#.#.#########v#
#.#...#...#...###...>.#
#.#.#v#######v###.###v#
#...#.>.#...>.>.#.###.#
#####v#.#.###v#.#.###.#
#.....#...#...#.#.#...#
#.#########.###.#.#.###
#...###...#...#...#.###
###.###.#.###v#####v###
#...#...#.#.>.>.#.>.###
#.###.###.#.###.#.#v###
#.....###...###...#...#
#####################.#"""), 154)
unittest.main(exit=False)
with open('input23.txt') as file:
data = file.read()
# print("Part 1:", parse1(data))
print("Part 2:", parse2(data))