Jake Pullen
75 lines
2.4 KiB
Python
75 lines
2.4 KiB
Python
testing = 0
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if not testing:
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with open(r"2024/06\input.txt", "r") as file:
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input = file.read()
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else:
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input = """....#.....
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.........#
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..........
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..#.......
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.......#..
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..........
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.#..^.....
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........#.
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#.........
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......#..."""
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OBSTACLE = "#"
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# first we should turn the input into a list of lists so we can use grid references
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split_input = input.split("\n")
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grid = [list(x) for x in split_input]
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ROWS = len(grid)
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COLUMNS = len(grid[0])
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# for x in grid:
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# print(x)
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# we need to find the starting position
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# our starting position is the only '^' in the grid
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for x in range(len(grid)):
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for y in range(len(grid[x])):
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if grid[x][y] == "^":
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position = (x, y)
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break
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#print('start at',position)
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# We start by travelling north until we hit an obstacle '#'
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# then we turn right and travel east until we hit an obstacle
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# we keep turning right and travelling until we hit an obstacle
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# once we make it off the grid we stop
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# count how many unique squares we visit
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loops = 0
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for row in range(ROWS):
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for col in range(COLUMNS):
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directions = [(-1, 0), (0, 1), (1, 0), (0, -1)] # North, East, South, West
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direction_index = 0 # Start by moving north
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x, y = position
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visited = set()
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visited_with_direction = set() # used for loop detection
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while True:
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visited.add((x, y))
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if (x, y, direction_index) in visited_with_direction:
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#print(f"Loop detected at ({x}, {y}) in direction {directions[direction_index]}")
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loops += 1
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break
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visited_with_direction.add((x, y, direction_index))
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dx, dy = directions[direction_index]
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new_x, new_y = x + dx, y + dy
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# if new position is off the grid, we stop
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if (new_x < 0 or new_x >= len(grid) or new_y < 0 or new_y >= len(grid[0])):
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#print(f"Moved off the grid to ({new_x}, {new_y}), stopping")
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break
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# if we hit an obstacle, we turn right
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elif (grid[new_x][new_y] == OBSTACLE or (new_x, new_y) == (row,col)):
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direction_index = (direction_index + 1) % 4 # Turn right
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#print(f"Hit obstacle at ({new_x}, {new_y}), turning right to direction {directions[direction_index]}")
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else:
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x, y = new_x, new_y
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#print(f"Moved to ({x}, {y})")
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print('part 1 answer',len(visited))
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print('part 2 answer',loops)
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