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