n=4的一些解决方案:
..0..1..1....0..1..3....0..1..1....0..1..1....0..1..3....0..0..1....0..1..0
..1..1..1....0..0..2....2..0..1....2..0..0....1..3..1....0..0..0....1..1..1
..3..1..1....2..2..2....3..2..3....2..2..0....3..1..0....0..0..1....3..3..3
..2..0..0....2..3..2....1..3..3....0..0..2....3..1..1....0..0..1....1..1..3