We present a novel approach for computing all maximum consecutive subsums in a sequence of positive integers in near-linear time. Solutions for this problem over binary sequences can be used for reporting existence of Parikh vectors in a bit string. Recently, several attempts have been made to build indexes for all Parikh vectors of a binary string in subquadratic time. However, no algorithm is known to date which can beat by more than a polylogarithmic factor the naive Θ(n2) procedure. We show how to construct a (1+ϵ)-approximate index for all Parikh vectors of a binary string in O(nlog^2n/log(1+ϵ), for any constant ϵ>0. Such index is approximate, in the sense that it leaves a small chance for false positives (no false negatives are possible). However, we can tune the parameters of the algorithm so that we can strictly control such a chance of error while still guaranteeing strong subquadratic running time.
Approximating the maximum consecutive subsums of a sequence
CICALESE, Ferdinando;
2014
Abstract
We present a novel approach for computing all maximum consecutive subsums in a sequence of positive integers in near-linear time. Solutions for this problem over binary sequences can be used for reporting existence of Parikh vectors in a bit string. Recently, several attempts have been made to build indexes for all Parikh vectors of a binary string in subquadratic time. However, no algorithm is known to date which can beat by more than a polylogarithmic factor the naive Θ(n2) procedure. We show how to construct a (1+ϵ)-approximate index for all Parikh vectors of a binary string in O(nlog^2n/log(1+ϵ), for any constant ϵ>0. Such index is approximate, in the sense that it leaves a small chance for false positives (no false negatives are possible). However, we can tune the parameters of the algorithm so that we can strictly control such a chance of error while still guaranteeing strong subquadratic running time.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
