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Using hashing to solve the dictionary problem

par Iacono, John ;Pǎtraşcu, Mihai
Référence Proceedings of the annual ACM-SIAM Symposium on Discrete Algorithms, page (570-582)
Publication Publié, 2012

Article révisé par les pairs

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Résumé :

We consider the dictionary problem in external memory and improve the update time of the well-known buffer tree by roughly a logarithmic factor. For any λ ≥ max{lg lg n, logM/B(n/B)}, we can support updates in time O(λ/B) and queries in sublogarithmic time, O(log λ n). We also present a lower bound in the cell-probe model showing that our data structure is optimal. In the RAM, hash tables have been use to solve the dictionary problem faster than binary search for more than half a century. By contrast, our data structure is the first to beat the comparison barrier in external memory. Ours is also the first data structure to depart convincingly from the indivisibility paradigm.