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arXiv 1107.2639math.CO
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部分拉丁方的Hall条件

Hall's Condition for Partial Latin Squares

A. J. W. Hilton, E. R. Vaughan

摘要:

Hall条件是部分拉丁方可完备的必要条件。Hilton和Johnson证明了对于一个部分拉丁方,其填充单元形成一个矩形,Hall条件等价于Ryser条件,这是可完全性的一个充要条件。我们给什么可以被视为一个扩展的Ryser定理,通过显示,部分拉丁方的填充细胞形成一个矩形,其中有最多一个空细胞在每列的矩形,霍尔的条件是一个充要条件的可完成性。部分拉丁方是否可完备的判定问题是NP-完全的。证明了满足Hall条件的部分拉丁方是否可完备的问题是NP-困难的。

英文摘要:

Hall's Condition is a necessary condition for a partial latin square to be completable. Hilton and Johnson showed that for a partial latin square whose filled cells form a rectangle, Hall's Condition is equivalent to Ryser's Condition, which is a necessary and sufficient condition for completability. We give what could be regarded as an extension of Ryser's Theorem, by showing that for a partial latin square whose filled cells form a rectangle, where there is at most one empty cell in each column of the rectangle, Hall's Condition is a necessary and sufficient condition for completability. It is well-known that the problem of deciding whether a partial latin square is completable is NP-complete. We show that the problem of deciding whether a partial latin square that is promised to satisfy Hall's Condition is completable is NP-hard.

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