Problem Detail: Let $L$ be a regular language. Prove that: $L_{+–}=left{w: exists_u |u|=2|w| wedge wuin Lright}$ $L_{++-}=left{w: exists_u 2|u|=|w| wedge wuin L right}$ $L_{-+-}=left{w:exists_{u,v} |u|=|w|=|v| wedge uwvin Lright}$ are regular and: $L_{+-+}=left{ uv:exists_w |u|=|w|=|v| wedge uwvin L right}$ is not Read More …
Month: February 2017
[Solved]: Is star closure of reverse of language equivalent to reverse of closure of that language
Problem Detail: is the following true $ (L^R)^* = (L^*)^R $ I tried the following to prove it true. let u,v belong to L then $ L^* = { u,v, uu, vv, uv, vu … } $ and $ (L^*)^R = Read More …
[Solved]: Why is the unary representation of a number exponentially larger than a base k representation of it?
Problem Detail: According to a book I am reading, the unary representation of a number exponentially larger than a base k representation of it. I, however, feel that the unary representation should scale linearly with the input. After all, 1 is Read More …
[Solved]: Provide some help regarding the “Dining Philosophers Problem”?
Problem Detail: I have an assignment based on operating systems and the question is divided into two sub-questions. The first is: Prove any seating arrangement of lefties and righties, with at least one of each avoiding deadlock. The second: Prove any Read More …
[Solved]: Good mathematical book on algorithms
Problem Detail: I’m a sucker for mathematical elegance and rigour, and now am looking for such literature on algorithms and algorithm analysis. Now, it doesn’t matter much to me what algorithms are covered, but very much how they are presented and Read More …
[Solved]: use of unconditional transfer of control instruction
Problem Detail: I did not understand why unconditional transfer of control instruction is used in cpu.So if we already know we have to jump to an instruction and skip some instruction irrespective of any condition then why do we not avoid Read More …
[Solved]: Doron ZEILBERGER’s P = NP computer proof
Problem Detail: In 2009 Doron has published a paper stating “Using 3000 hours of CPU time on a CRAY machine, we settle the notorious P vs. NP problem in the affirmative, by presenting a “polynomial” time algorithm for the NP-complete subset Read More …
[Solved]: Why isn’t converting from an NFA to a DFA working?
Problem Detail: I am just beginning to learn computation theory. I wrote up a non-deterministic finite automata that accepts strings that contain the substring “abba”: I tried to convert it to a DFA by putting together sets of states in the Read More …
[Solved]: Initial Algebra example
Problem Detail: If the definition of Initial Algebra is: “An object is initial if there exists a unique morphism from the object to every object in the category” Why do we need such object, and could any one give an example Read More …
[Solved]: Fast Poisson quantile computation
Problem Detail: I am seeking a fast algorithm to compute the following function, a quantile of the Poisson distribution: $$f(n, lambda) = e^{-lambda} sum_{k=0}^{n} frac{lambda^k}{k!} $$ I can think of an algorithm in $O(n)$, but considering the structure of the series, Read More …