Advent of Code 2023 - December 10th
Rob van der Leek
Posted on December 12, 2023
In this series, I'll share my progress with the 2023 version of Advent of Code.
Check the first post for a short intro to this series.
You can also follow my progress on GitHub.
December 10th
The puzzle of day 10 is a monster. It appears to be much easier than it is (it's a hair-puller). So far I've only solved the first part, and for that I needed to increase the recursion limit 😨 UPDATE: I've also solved part two.
My pitfall for this puzzle: I was convinced a backtrack solution was the way to go for this puzzle. However, the input does not work for the default Python recursion depth. Increasing the recursion depth limit feels bad, but I don't have the time to look into other ways to solve the puzzle. Part two also cost me a lot of time. This is not my kind of puzzle 😉
Solution here, do not click if you want to solve the puzzle first yourself
#!/usr/bin/env python3
import math
import sys
with open('input.txt') as infile:
lines = infile.readlines()
grid = []
S = None
for x, line in enumerate(lines):
line_pipes = [c for c in line.strip()]
grid.append(line_pipes)
if 'S' in line_pipes:
S = (x, line_pipes.index('S'))
def get_pipe(y, x):
if y < 0 or y >= len(grid) or x < 0 or x >= len(grid[y]):
return None
return grid[y][x]
visited = []
def walk(pos, trail):
if pos in visited:
if grid[pos[0]][pos[1]] == 'S' and len(trail) > 2:
return trail
else:
return None
else:
visited.append(pos)
result = None
if get_pipe(pos[0], pos[1]) in ['-', 'L', 'F', 'S'] and \
get_pipe(pos[0], pos[1] + 1) in ['-', 'J', '7', 'S']:
result = walk((pos[0], pos[1] + 1), trail + [(pos[0], pos[1] + 1)])
if not result and get_pipe(pos[0], pos[1]) in ['|', '7', 'F', 'S'] and \
get_pipe(pos[0] + 1, pos[1]) in ['|', 'L', 'J', 'S']:
result = walk((pos[0] + 1, pos[1]), trail + [(pos[0] + 1, pos[1])])
if not result and get_pipe(pos[0], pos[1]) in ['-', 'J', '7', 'S'] and \
get_pipe(pos[0], pos[1] - 1) in ['-', 'L', 'F', 'S']:
result = walk((pos[0], pos[1] - 1), trail + [(pos[0], pos[1] - 1)])
if not result and get_pipe(pos[0], pos[1]) in ['|', 'L', 'J', 'S'] and \
get_pipe(pos[0] - 1, pos[1]) in ['|', '7', 'F', 'S']:
result = walk((pos[0] - 1, pos[1]), trail + [(pos[0] - 1, pos[1])])
return result
sys.setrecursionlimit(14000)
trail = walk(S, [])
print(math.floor(len(trail) / 2))
def replace_S(grid, trail):
after = trail[0]
before = trail[-2]
if before[0] > S[0] and before[1] == S[1] and after[0] == S[0] and after[1] > S[1]:
grid[S[0]][S[1]] = 'F'
elif before[0] < S[0] and before[1] == S[1] and after[0] == S[0] and after[1] > S[1]:
grid[S[0]][S[1]] = 'L'
elif before[0] == S[0] and before[1] < S[1] and fter[0] > S[0] and after[1] == S[1]:
grid[S[0]][S[1]] = '7'
elif before[0] < S[0] and before[1] == S[1] and after[0] == S[0] and after[1] < S[1]:
grid[S[0]][S[1]] = 'J'
else:
grid[S[0]][S[1]] = '|'
replace_S(grid, trail)
enclosed = 0
for idx_y, row in enumerate(grid):
in_loop = in_l = in_f = False
for idx_x, col in enumerate(grid[idx_y]):
if (idx_y, idx_x) in trail:
if in_f:
if col == 'J':
in_loop = not in_loop
in_f = False
elif col == '7':
in_f = False
if in_l:
if col == '7':
in_loop = not in_loop
in_l = False
elif col == 'J':
in_l = False
elif col in ['|']:
in_loop = not in_loop
elif col == 'L':
in_l = True
elif col == 'F':
in_f = True
else:
if in_loop:
enclosed += 1
print(enclosed)
That's it! See you again tomorrow!
Posted on December 12, 2023
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