Browsing by Author "Hirschberg, D.S."
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Item An Information Theoretic Lower Bound for the Longest Common Subsequence Problem(1977-04-20) Hirschberg, D.S.We shall derive a lower on the number of "less-than-equal-greater than" comparisons required to solve the longest common subsequence (LCS) problem.Item A Lower Worst-Case Complexity for Searching a Dictionary(1978-07-20) Hirschberg, D.S.It is shown that k(p+3)/2 + p-2 letter comparisons suffice to determine whether a word is a member of a lexicographically ordered dictionary containing 2p-1 words of length k. This offers a potential savings (compared to worst case complexity of binary search) that asymptotically approaches 50 percent.Item On the Complexity of Vector Searching(1978-06-20) Hirschberg, D.S.The vector searching problem is, given k-vector A (a k-vector) is a vector that has k components, over the integers) and given a set B of n distinct k-vectors, to determine whether or not A is a member of set B. Comparisons between components yielding "greater than-equal-less than" results are permitted. It is shown that if the vectors in B are unordered then nk comparisons are necessary and sufficient. In the case when the vectors in B are ordered, it is shown that [log n] + k comparisons are necessary and, for n≥4k, k[log(n/k)] + 2k-1 comparisons are sufficient.Item A Parallel Graph Algorithm for Finding Connected Components(1975-10-20) Hirschberg, D.S.A parallel program is presented that determines the connected components of an undirected graph in time 0(log2n) using n2 processors. It is assumed that the processors have access to common memory. Simultaneous access to the same location is permitted for fetch, but not store, instructions.