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