b***k
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Allens (ffff) 于 (Mon Jan 18 21:16:40 2010, 美东) 提到:
Consider a cartesian product over n given finite sets,
X=X1×X2×。。。×Xn
Try to prove that X cannot be partitioned into less than 2^n subsets,
each of which is in form of Y1×Y2×。。。×Yn, Y1...Yn are proper subsets
of X1...Xn, respectively.
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netghost (Up to Isomorphism) 于 (Wed Jan 20 07:37:21 2010, 美东) 提到:
Let's say there is a particular subset with the form
Z1 X |
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