Indexing Straight-Line Programs∗
نویسندگان
چکیده
Straight-line programs offer powerful text compression by representing a text T [1, u] in terms of a context-free grammar of n rules, so that T can be recovered in O(u) time. However, the problem of operating the grammar in compressed form has not been studied much. We present the first grammar representation able of extracting text substrings, and of searching the text for patterns, in time o(n). Its size is of the same order of that of a plain SLP representation, and it can be of independent interest for other grammar-based problems. We also give some byproducts on representing binary relations.
منابع مشابه
Fully Compressed Pattern Matching Algorithm for Balanced Straight-Line Programs
We consider a fully compressed pattern matching problem, where both text T and pattern P are given by its succinct representation, in terms of straight-line programs and its variant. The length of the text T and pattern P may grow exponentially with respect to its description size n and m, respectively. The best known algorithm for the problem runs in O(nm) time using O(nm) space. In this paper...
متن کاملFaster fully compressed pattern matching algorithm for a subclass of straight-line programs
We show an efficient pattern-matching algorithm for strings that are succinctly described in terms of straight-line programs, in which the constants are symbols and the only operation is the concatenation. In this paper, both text T and pattern P are given by straight-line programs T and P. The length of the text T (pattern P , resp.) may grow exponentially with respect to its description size ...
متن کاملImplicit Computation: an Output-Polynomial Algorithm for Evaluating Straight-Line Programs
theory of computation, randomized algorithms, straight-line programs, output-polynomial algorithms Inputless straight-line programs using addition, subtraction and multiplication are considered. An output-polynomial algorithm is given for computing the output of such a program. The program runs in time polynomial in the length of the program and the length of its output. As a consequence, even ...
متن کاملReal roots of univariate polynomials and straight line programs
We give a new proof of the NP-hardness of deciding the existence of real roots of an integer univariate polynomial encoded by a straight line program based on certain properties of the Tchebychev polynomials. These techniques allow us to prove some new NP-hardness results related to real root approximation for polynomials given by straight line programs.
متن کاملSemantics Sensitive Sampling for Probabilistic Programs
We present a new semantics sensitive sampling algorithm for probabilistic programs, which are “usual” programs endowed with statements to sample from distributions, and condition executions based on observations. Since probabilistic programs are executable, sampling can be performed by repeatedly executing them. However, in the case of programs with a large number of random variables and observ...
متن کامل