My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add solution for 2024/06
+59
+59
2024/day06.py
+59
2024/day06.py
···
1
+
import fileinput
2
+
from utils import Point, N, S, E, W
3
+
4
+
5
+
DIRS = [S, E, N, W]
6
+
7
+
def simulate(board, start, obs=None):
8
+
BOARD[obs] = '#'
9
+
p = start
10
+
d = 0
11
+
seen = set()
12
+
13
+
while True:
14
+
if (p, d) in seen:
15
+
# Loop detected.
16
+
BOARD[obs] = '.'
17
+
return None
18
+
19
+
seen.add((p, d))
20
+
21
+
np = p + DIRS[d]
22
+
if BOARD.get(np) == '#':
23
+
d = (d + 1) % 4
24
+
elif BOARD.get(np) is None:
25
+
break
26
+
else:
27
+
p += DIRS[d]
28
+
29
+
BOARD[obs] = '.'
30
+
return set(p for p, _ in seen)
31
+
32
+
# Read problem input.
33
+
BOARD = {}
34
+
for y, line in enumerate(fileinput.input()):
35
+
for x, c in enumerate(line.strip()):
36
+
p = Point(x, y)
37
+
BOARD[p] = c
38
+
if c == '^':
39
+
START = p
40
+
41
+
# Solve part 1.
42
+
seen = simulate(BOARD, START)
43
+
print("Part 1:", len(seen))
44
+
45
+
# Solve part 2.
46
+
candidates = set()
47
+
for x in seen:
48
+
for n in x.neighbours():
49
+
candidates.add(n)
50
+
51
+
part_2 = 0
52
+
for p in candidates:
53
+
if p not in seen or BOARD.get(p) != '.':
54
+
continue
55
+
if simulate(BOARD, START, obs=p) is None:
56
+
part_2 += 1
57
+
58
+
print("Part 2:", part_2)
59
+