Computer Science – Data Structures and Algorithms
Scientific paper
2009-11-17
Computer Science
Data Structures and Algorithms
20 pages, 5 figures
Scientific paper
Motivated by a concrete problem and with the goal of understanding the sense in which the complexity of streaming algorithms is related to the complexity of formal languages, we investigate the problem Dyck(s) of checking matching parentheses, with $s$ different types of parenthesis. We present a one-pass randomized streaming algorithm for Dyck(2) with space $\Order(\sqrt{n}\log n)$, time per letter $\polylog (n)$, and one-sided error. We prove that this one-pass algorithm is optimal, up to a $\polylog n$ factor, even when two-sided error is allowed. For the lower bound, we prove a direct sum result on hard instances by following the "information cost" approach, but with a few twists. Indeed, we play a subtle game between public and private coins. This mixture between public and private coins results from a balancing act between the direct sum result and a combinatorial lower bound for the base case. Surprisingly, the space requirement shrinks drastically if we have access to the input stream in reverse. We present a two-pass randomized streaming algorithm for Dyck(2) with space $\Order((\log n)^2)$, time $\polylog (n)$ and one-sided error, where the second pass is in the reverse direction. Both algorithms can be extended to Dyck(s) since this problem is reducible to Dyck(2) for a suitable notion of reduction in the streaming model.
Magniez Frederic
Mathieu Charles
Nayak Ashwin
No associations
LandOfFree
Recognizing well-parenthesized expressions in the streaming model does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Recognizing well-parenthesized expressions in the streaming model, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Recognizing well-parenthesized expressions in the streaming model will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-650624