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def read_grid(filename):
with open(filename, 'r') as f:
return [line.strip() for line in f.readlines()]
def get_word_at(grid, x, y, dx, dy, length):
if not (0 <= x + (length-1)*dx < len(grid[0]) and 0 <= y + (length-1)*dy < len(grid)):
return ""
return ''.join(grid[y + i*dy][x + i*dx] for i in range(length))
def count_xmas(grid):
directions = [
(1,0), (0,1), (1,1), (-1,1), # right, down, diagonal-right, diagonal-left
(-1,0), (0,-1), (-1,-1), (1,-1) # left, up, diagonal-left-up, diagonal-right-up
]
count = 0
for y in range(len(grid)):
for x in range(len(grid[0])):
for dx, dy in directions:
if get_word_at(grid, x, y, dx, dy, 4) == "XMAS":
count += 1
return count
def check_xmas_pattern(grid, x, y):
# Check both diagonals for MAS or SAM
patterns = 0
diagonals = [
[(x-1, y-1), (x, y), (x+1, y+1)], # top-left to bottom-right
[(x+1, y-1), (x, y), (x-1, y+1)] # top-right to bottom-left
]
def is_valid_pos(pos):
return 0 <= pos[0] < len(grid[0]) and 0 <= pos[1] < len(grid)
def get_string(positions):
if not all(is_valid_pos(pos) for pos in positions):
return ""
return ''.join(grid[y][x] for x, y in positions)
for d1 in diagonals:
for d2 in diagonals:
if d1 == d2:
continue
s1 = get_string(d1)
s2 = get_string(d2)
if ((s1 == "MAS" or s1 == "SAM") and
(s2 == "MAS" or s2 == "SAM")):
patterns += 1
return patterns // 2 # Each valid pattern is counted twice due to diagonal combinations
def count_xmas_patterns(grid):
total = 0
for y in range(len(grid)):
for x in range(len(grid[0])):
total += check_xmas_pattern(grid, x, y)
return total
# Read input and solve both parts
grid = read_grid("input.txt")
# Part 1
print(str(count_xmas(grid)))
# Part 2
print(str(count_xmas_patterns(grid))) |