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100 lines
3.0 KiB
Python
100 lines
3.0 KiB
Python
DIRECTIONS = {
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"^": 0 - 1j, # up
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">": 1 + 0j, # right
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"v": 0 + 1j, # down
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"<": -1 + 0j, # left
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}
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def find_start_pos(grid):
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for y, row in enumerate(grid):
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for x, _ in enumerate(row):
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if grid[y][x] == "@":
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return complex(x, y)
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def get_pos(grid, pos):
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x, y = int(pos.real), int(pos.imag)
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if 0 <= x < len(grid[0]) and 0 <= y < len(grid):
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return grid[y][x]
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return None
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def set_pos(grid, pos, val):
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x, y = int(pos.real), int(pos.imag)
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grid[y][x] = val
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def debug_print(grid, move):
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print("Move ", move)
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for row in grid:
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print("".join(row))
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def push(grid, pos, movement):
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direction = DIRECTIONS[movement]
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start_pos = pos + direction
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# Find the end pos of a consecutive "O" chain
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end_pos = start_pos
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while get_pos(grid, end_pos + direction) == "O":
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end_pos += direction
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if get_pos(grid, end_pos + direction) == ".":
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if movement == ">":
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start_x, end_x = int(start_pos.real), int(end_pos.real)
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y = int(start_pos.imag)
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for i in range(end_x, start_x - 1, -1):
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grid[y][i+1] = "O" # shift "O" to the right
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grid[y][start_x] = "."
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elif movement == "<":
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start_x, end_x = int(start_pos.real), int(end_pos.real)
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y = int(start_pos.imag)
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for i in range(start_x, end_x + 1):
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grid[y][i+1] = "O" # shift "O" to the left
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grid[y][start_x] = "."
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elif movement == "v":
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start_y, end_y = int(start_pos.imag), int(end_pos.imag)
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x = int(start_pos.real)
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for i in range(start_y, end_y + 1):
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grid[i+1][x] = "O" # shift "O" down
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grid[start_y][x] = "."
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elif movement == "^":
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start_y, end_y = int(start_pos.imag), int(end_pos.imag)
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x = int(start_pos.real)
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for i in range(end_y, start_y - 1, -1):
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grid[i+1][x] = "O" # shift "O" up
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grid[start_y][x] = "."
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def main(content):
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grid, movements = content.split("\n\n")
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grid = [list(x) for x in grid.split("\n")]
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movements = movements.replace("\n", "")
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pos = find_start_pos(grid)
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for movement in movements:
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new_pos = pos + DIRECTIONS[movement]
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v = get_pos(grid, new_pos)
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match v:
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case ".":
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set_pos(grid, pos, ".")
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set_pos(grid, new_pos, "@")
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pos = new_pos
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case "O":
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push(grid, pos, movement)
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if get_pos(grid, new_pos) == ".":
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set_pos(grid, new_pos, "@")
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set_pos(grid, pos, ".")
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pos = new_pos
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case "#": pass
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case c: raise RuntimeError("This should never happen", c)
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debug_print(grid, movement)
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if __name__ == "__main__":
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import sys
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infile = sys.argv[1] if len(sys.argv) > 1 else "example.txt"
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with open(infile) as f:
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content = f.read()
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main(content)
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