n=4的一些解决方案:
..0..1..2..0..2..0..2....0..1..2..1..2..0..1....0..1..2..1..2..1..2
..2..0..1..2..0..2..1....2..0..1..0..1..2..0....2..0..1..2..0..2..1
..0..2..0..1..2..0..2....0..2..0..1..0..1..2....1..2..0..1..2..0..2
..1..0..1..2..0..2..0....1..0..1..2..1..2..0....0..1..2..0..1..2..1