Author: ignougroup

Problem Detail: What does the notation co- mean when prefixing co-NP, co-RE (recursively enumerable), or co-CE (computably enumerable) ? Asked By : Vanwaril Answered By : Gilles Often, in mathematical terminology, the prefix co- refers to a dual in some sense. For complexity Read More …

Problem Detail:  A) Solve this recurrence where $T(0)=0$ and write it in O-notation: $T(n)= {2 over n} (T(0)+T(1)+…+T(n-1))+c$ So, I started to calculate: $T(1)=2(0)+c=c$ $T(2)=1(0+c)+c=2c$ and so on, which gives me that $T(n)=nc$ This I can prove by induction: $(n-1) Read More …

Problem Detail: A computer has 2 GB of RAM of which the operating system occupies 256 MB. The processes are all 128 MB (for simplicity) and have the same characteristics. If the goal is 99% CPU utilization, what is the maximum Read More …

Problem Detail: In Knuth’s original paper on $LR(k)$ grammars, he proved that the decision problem “Given a CFG $G$, is there a $k$ such that $G$ is an $LR(k)$ grammar?” is undecidable. Is there a similar result showing that it is Read More …

Problem Detail: What is the complexity of the following problem? Given a mixed (some edges directed, some undirected) graph, assign a direction to all the undirected edges to make the graph contain a cycle. It doesn’t “feel” like an NP-hard problem, Read More …

Problem Detail: I’m trying to write an algorithm that detects the most common subset of at least size $k$, from a collection of sets. If there are ties for the most common subset, I want the one of them whose size Read More …

Problem Detail: I’m currently creating a program to analyse the pathological cases of Quicksort. Namely, the transition of complexity from $O(n^2)$ to $O(n log n)$ as a data set gets less ordered. Since Quicksort is a value-based algorithm, the choice of Read More …

Problem Detail: I’m trying to understand the equivalence in expressive power of formal grammars whose rules take the form: $$ alpha rightarrow beta $$ where $ |alpha| leq |beta| $ (called a monotonic grammar), and grammars whose rules take the form: Read More …

Problem Detail: I’ve been studying for an exam I have tomorrow, and I was looking through some previous sample exam questions, when I came across this problem: Give a non-regular language $L$ such that $L cup L^R$ is regular. I’ve been Read More …

Problem Detail: I am trying to understand the concept of logical to physical addressing. I am given 72 physical addresses (0-71) with values A virtual address = 2^(p+w) p = page bits w = word bits I know the page table Read More …