Problem Detail: Is there a need for $Lsubseteq Sigma^*$ to be infinite to be undecidable? I mean what if we choose a language $L’$ be a bounded finite version of $Lsubseteq Sigma^*$, that is $|L’|leq N$, ($N in mathbb{N}$), with $L’ Read More …
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What are lattices used for?
Problem Detail: Wikipedia says: Complete lattices appear in many applications in mathematics and computer science Is it just referring to the fact that the standard Boolean algebra used in computation is a complete lattice? Is there anything we gain by working Read More …
how to draw a complement of a Turing Machine?
Problem Detail: I am now pretty confident on how I would turn something into a Turing Machine. Now my question is how do you convert TM into a complement of a Turing Machine. From what I can remember in Finite Automata, Read More …
What is the difference between decidability and computability?
Problem Detail: If they are different, what are the typical problems in each that do not fall on the other category? Or are the mutually exclusive or does one completely capture the other? Asked By : sdfasdgasg Answered By : Kaveh A function Read More …
How is the rule 110 Turing complete?
Problem Detail: I’ve read the wikipedia page for rule 110 in cellular automata, and I more or less know how they work (a set of rules decides where to draw the next 1 or 0). I’ve just read they’re Turing complete, Read More …
“NP-complete” optimization problems
Problem Detail: I am slightly confused by some terminology I have encountered regarding the complexity of optimization problems. In an algorithms class, I had the large parsimony problem described as NP-complete. However, I am not exactly sure what the term NP-complete Read More …
Constructing PDA for $a^{2n} b^{3n}$
Problem Detail: So I have been given the task of creating an PDA that recognises the language ${a^{2n} b^{3n} mid n = 0,1,2,dots}$. Am I right in thinking that it needs to have at least 3 times number of $b$’s than Read More …
Bellman-Ford algorithm – Why can edges be updated out of order?
Problem Detail: The Bellman-Ford algorithm determines the shortest path from a source $s$ to all other vertices. Initially the distance between $s$ and all other vertices is set to $infty$. Then the shortest path from $s$ to each vertex is computed; Read More …
Why is the halting problem unsolvable by a turing machine?
Problem Detail: So my knowledge of CS is amateurish at best but to me, logically, it seems like the halting problem is solvable. So any human can determine if a problem halts with rigorous inspection, so why can’t a very advanced, Read More …
Parallel algorithm for finding the maximum in $log n$ time using $n / log n$ processors
Problem Detail: We were presented in class with an algorithm for finding the maximum in an array in parallel in $O(1)$ time complexity with $n^2$ computers. The algorithm was: Given an array A of length n: Make a flag array B Read More …
