n=7的一些解决方案:
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....1....0....1....1....1....1....1....1....1....0....0....1....1....1
..0....0....0....1....1....2....0....2....2....0....0....1....0....0....1....2
..0....1....0....1....0....0....1....2....1....2....2....0....0....0....2....1
..1....2....0....2....1....2....1....1....0....1....1....1....0....0....0....1
..0....1....0....1....0....1....0....0....0....1....0....0....0....1....1....0
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0