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キーワード:
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要旨:
The complexity of maintaining a set under the operations {\sf Insert}, {\sf Delete} and {\sf FindMin} is considered. In the comparison model it is shown that any randomized algorithm with expected amortized cost $t$ comparisons per {\sf Insert} and {\sf Delete} has expected cost at least $n/(e2^{2t})-1$ comparisons for {\sf FindMin}. If {\sf FindMin} 474 is replaced by a weaker operation, {\sf FindAny}, then it is shown that a randomized algorithm with constant expected cost per operation exists, but no deterministic algorithm. Finally, a deterministic algorithm with constant amortized cost per operation for an offline version of the problem is given.
