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Running
File size: 2,567 Bytes
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def parse_input(file):
with open(file, 'r') as f:
grid = [list(line.strip()) for line in f.readlines()]
return grid
def find_guard_start(grid):
directions = {'^': (0, -1), '>': (1, 0), 'v': (0, 1), '<': (-1, 0)}
for y, row in enumerate(grid):
for x, cell in enumerate(row):
if cell in directions:
return (x, y), directions[cell]
return None, None
def turn_right(direction):
right_turns = {(0, -1): (1, 0), (1, 0): (0, 1), (0, 1): (-1, 0), (-1, 0): (0, -1)}
return right_turns[direction]
def move(position, direction):
return position[0] + direction[0], position[1] + direction[1]
def is_within_bounds(position, grid):
x, y = position
return 0 <= x < len(grid[0]) and 0 <= y < len(grid)
def simulate_guard(grid):
start_pos, direction = find_guard_start(grid)
visited = set()
position = start_pos
while is_within_bounds(position, grid):
visited.add(position)
next_position = move(position, direction)
if is_within_bounds(next_position, grid) and grid[next_position[1]][next_position[0]] == '#':
direction = turn_right(direction)
else:
position = next_position
return visited
def simulate_with_obstruction(grid, obstruction_pos):
start_pos, direction = find_guard_start(grid)
visited = set()
position = start_pos
direction_map = {(-1, 0): '<', (0, -1): '^', (1, 0): '>', (0, 1): 'v'}
while is_within_bounds(position, grid):
if position == obstruction_pos:
return False # Obstruction is here, can't move
if (position, direction) in visited:
return True # Loop detected
visited.add((position, direction))
next_position = move(position, direction)
if is_within_bounds(next_position, grid) and (grid[next_position[1]][next_position[0]] == '#' or next_position == obstruction_pos):
direction = turn_right(direction)
else:
position = next_position
return False
def find_loop_positions(grid):
loop_positions = 0
for y, row in enumerate(grid):
for x, cell in enumerate(row):
if cell == '.' and (x, y) != find_guard_start(grid)[0]:
if simulate_with_obstruction(grid, (x, y)):
loop_positions += 1
return loop_positions
file = "input.txt"
grid = parse_input(file)
# Part 1
visited_positions = simulate_guard(grid)
print(len(visited_positions))
# Part 2
loop_positions = find_loop_positions(grid)
print(loop_positions) |