Author: ignougroup

Problem Detail: I know that there are non-regular languages, so that $L^*$ is regular, but all examples I can find are context-sensitive but not context free. In case there are none how do you prove it? Asked By : Simon S Answered Read More …

Problem Detail: Suppose the datatype for a BST is defined as follows (in SML) datatype ‘a bst_Tree = Empty | Node of (int * ‘a) * ‘a bst_Tree * ‘a bst_Tree; So there are two cases one in which the BST Read More …

Problem Detail: The underlying question: What does lambda calculus do for us that we can’t do with the basic function properties and notation generally learned in middle school algebra? First of all, what does abstract mean in the context of lambda Read More …

Problem Detail: Is there an efficient way to find the longest path between any two nodes in a tree. Given that edges can have negative weights. I know about the diameter problem which finds the longest path in a graph with Read More …

Problem Detail: We have many problems, like factorization, that are strongly conjectured, but not proven, to be outside P. Are there any questions with the opposite property, namely, that they are strongly conjectured but not proven to be inside P? Asked Read More …

Problem Detail: I took an algorithms class on Coursera. The professor in the video about hash tables said that What’s true is that for non-pathological data, you will get constant time operations in a properly implemented hash table. What does “non-pathological Read More …

Problem Detail: I’m reading Garey & Johnsons “Computers and Intractability” and I’m at the part “Some techniques for solving NP-Completeness”. Here’s the text about Proof by Restriction: Proof by restriction is the simplest, and perhaps most frequently applicable, of our three Read More …

Problem Detail: In a recent CACM article [1], the authors present an implementation for staged functions. They use the term as if it was well-known, and none of the references looks like an obvious introduction. They give a short explanation (emphasis Read More …

Problem Detail: Given a weighted digraph $G=V,E$, and a weight function, $d(u,v)$, one can normally use Dijkstra’s algorithm to obtain the shortest path. What I am interested in, is how to obtain the $2^{nd}$-shortest path, the $3^{rd}$-shortest, and so on. Questions: Read More …