Problem Detail: I’m having trouble intuitively understanding why PSPACE is generally believed to be different from EXPTIME. If PSPACE is the set of problems solvable in space polynomial in the input size $f(n)$, then how can there be a class of Read More …
Category: Uncategorized
does a DFA converted from NFA always contain 2^Q states?
Problem Detail: when converting an NFA to DFA, we create sub-sets of states in the NFA. does it mean that every DFA-converted-from-NFA contain 2^Q states? or if some sub-sets are unreachable then they are not included in it? Asked By : Tom Read More …
Is every regular language Turing-decidable, and how can we prove this?
Problem Detail: I know every regular language is Turing-acceptable, but does that imply it is Turing-decidable? Asked By : Iancovici Answered By : Mandar Mitra Every regular language is Turing-decidable and therefore Turing acceptable / recognisable (but note that Turing acceptable does not Read More …
Is the halting problem decidable for pure programs on an ideal computer?
Problem Detail: It’s fairly simple to understand why the halting problem is undecidable for impure programs (i.e., ones that have I/O and/or states dependent on the machine-global state); but intuitively, it seems that a pure program’s halting on an ideal computer Read More …
DFS – Proof of Correctness
Problem Detail: I’m currently studying the book “Introduction to Algorithms – Cormen”. Although a proof of correctness for the BFS algorithm is given, there isn’t one any for the DFS in the book. So I was courious about how it can Read More …
Why we do isomorphism, automorphism and homomorphism?
Problem Detail: What are the key differences between these three terms isomorphism, automorphism and homomorphism in simple layman language and why we do isomorphism, automorphism and homomorphism ? Asked By : Xara Answered By : Jernej Isomorphism formalizes the notion of equal graphs. Read More …
Push down automata for ${a^n b^n c^n | n ge 0}$
Problem Detail: I am learning about context free languages. I understand how ${a^n b^n c^n | n ge 0}$ can be shown to be not context free using the pumping lemma for CFL’s. Intuitively however it seems that a pushdown automata Read More …
What does a polynomial time reduction mean?
Problem Detail: I am having a little trouble understanding what is meant by a poly-time reduction. Suppose I have two algorithms $A$ and $B$ and then I say that $A$ is reducible to $B$. Does polytime reduction mean that the algorithm Read More …
What is the time complexity of generating n-th prime number?
Problem Detail: Say I want to find the n-th prime. Is there an algorithm to directly calculate it or must I do with sieving? I know always calculate the next prime with a sieve principle, but what if I want the Read More …
When are binary trees better than hashtables in real world applications?
Problem Detail: I am currently bushing up on my data structures and basic algorithms, part of that is the Binary Tree. I do understand the algorithms, and how to implement a binary search tree and such. I do so how smart Read More …
