送交者: lakeblue 于 December 06, 2009 14:38:38:
回答: 对2X2的board，每行和每列都含有奇数个marker的放法有2种，但每行和每列都含有偶数个marker的放法确有6种。 由 只是没想到而已 于 December 06, 2009 13:14:55:
There are also 2 ways that every row and every column contain an even number of markers: all filled and all empty. There are 12 ways for even-odd mix (0-1, 1-2, and 0-1-2). Altogether, there are 2+2+12 = 16 = 2^4 ways.
The result 2^[(N-1)^2] should also hold for the case of all even numbers. There is an even-odd symmetry here.