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Problem Detail: I am very familiar with Dijkstra and I have a specific question about the algorithm. If I have a huge graph, for example 3.5 billion nodes (all OpenStreetMap data) then I clearly wouldn’t be able to have the graph Read More …

Problem Detail: I know that sometimes we can use absolute values into the objective functions or constraints. Is it always possible to use them, anywhere ? Example of use of absolute values: Minimize |a+b+c| + |a-c| s.t. |a| + b > Read More …

Problem Detail: When I was a student, I saw a problem in a digital systems/logic design textbook, about N soldiers standing in a row, and want to shoot at the same time. A more difficult version of the problem was that Read More …

Problem Detail: I’ve studied something about the Kolmogorov Complexity, read some articles and books from Vitanyi and Li and used the concept of Normalized Compression Distance to verify the stilometry of authors (identify how each author writes some text and group Read More …

Problem Detail: The problem Some people are crossing a bridge. Each one takes a different time to pass. Assume the people are sorted by their passing time increasingly. These are the conditions of crossing the bridge: only 1 or 2 people Read More …

Problem Detail: Given the problem $EQ_{TM} = { langle M_1, M_2rangle mid M_1 text{ and } M_2 text{ are } TM, L_{M_1} = L_{M_2}}$, is it possible to prove that this is undecidable by using (a variant of) Rice theorem? I Read More …

Problem Detail: I read on the internet that it’s possible to reduce Clique to Vertex Cover. Almost everyone use this theorem: if a graph $G$ has a clique of size $k$ then the complement of $G$ has a vertex cover of Read More …

Problem Detail: Let $L_1, L_2$, two regular languages and the operations: $$Mix_1(L_1, L_2) ={ a_1b_1a_2b_2ldots a_nb_n | nge 0 land a_1,a_2,ldots ,a_n,b_1,b_2,ldots ,b_ninSigma land a_1a_2ldots a_nin L_1 , b_1b_2ldots b_nin L_2}$$ $$Mix_2(L_1, L_2) = { x_1y_1x_2y_2ldots x_ny_n | nge 0 land Read More …

Problem Detail: I was watching the videos from Skiena’s Computational Biology Lectures, which is also available at youtube. In those videos, the professor made a statement that, most of the problems posed to computer scientists by biologists were proved to be Read More …

Problem Detail: Question: Suppose I have a set of male people, and a function isAncestor(person1,person2) that checks whether person1 is an ancestor of person2 in O(1) time. Eg, isAncestor(grandfather, grandson) would return true. What are some fast algorithms for constructing a Read More …