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Top new questions this week:

"For small values of n, O(n) can be treated as if it's O(1)"

I've heard several times that for sufficiently small values of n, O(n) can be thought about/treated as if it's O(1). Example: The motivation for doing so is based on the incorrect idea that O(1) ...

asymptotics  
asked by rianjs 18 votes
answered by Eric Hughes 42 votes

Why do we believe that PSPACE ≠ EXPTIME?

I'm having trouble intuitively understanding why PSPACE is generally believed to be different from EXPTIME. If PSPACE is the set of problems solvable in space polynomial in the input size $f(n)$, ...

complexity-theory complexity-classes intuition  
asked by user25876 14 votes
answered by David Richerby 22 votes

Determining the minimum number of edges to add in order to be 3-connected

A graph $G$ is said to be $3$-connected if it has no $2$-vertex cutsets (i.e., at least three vertices must be deleted to disconnect the graph). As far as I know, it is possible to determine if a ...

algorithms graph-theory reference-request  
asked by Zachary Frenette 8 votes
answered by Chao Xu 3 votes

What is it called when two problems are similar?

Suppose that there are two problems $P$ and $Q$. How can I say that "solving $P$ is same thing with solving $Q$"? For instance, if $P$ is NP-Hard, then we can say "$P$ can be solved in polynomial ...

complexity-theory terminology  
asked by cagirici 7 votes
answered by Yuval Filmus 8 votes

Is $NP$ "minimal", i.e. does $\Pi\notin NP$ imply $\Pi$ is $NP$-hard?

Suppose $\Pi$ is a decidable decision problem. Does $\Pi\not \in NP$ imply $\Pi$ is $NP$-Hard? Edit: if we assume there exists $\Pi\in coNP\setminus NP$ then we are done. Can we refute the claim ...

complexity-theory np-hard complexity-classes np  
asked by A A 6 votes
answered by Yuval Filmus 3 votes

Find set of points with maximum distance inside given intervals?

Let $A$ be a set of $n$ closed intervals, $I_i$, with both extremes positive integers. Is there an efficient algorithm to find a set of $n$ points $P_i$, with $P_i \in I_i$, such that the minimum ...

algorithms optimization intervals  
asked by becko 5 votes
answered by Snick 0 votes

How to choose the maximum number of nodes (with constraints) from a graph

Consider a connected undirected acyclic graph $G$ with $n$ nodes and $n-1$ edges. The nodes have non-negative integer weights less than $n$. A positive integer $x$ is given and you want to choose at ...

algorithms graphs optimization trees  
asked by Lembik 5 votes
answered by Raphael 6 votes

Greatest hits from previous weeks:

Applying Expectation Maximization to coin toss examples

I've been self-studying the Expectation Maximization lately, and grabbed myself some simple examples in the process: From here: There are three coins $c_0$, $c_1$ and $c_2$ with $p_0$, $p_1$ and ...

probability-theory statistics  
asked by IcySnow 10 votes
answered by Nicholas Mancuso 8 votes

Does an Operating System inject its own machine code when you open a program?

I'm studying CPU's and I know how it reads a program from the memory and execute its instructions. I also understand that an OS separates programs in processes, and then alternate between each one so ...

operating-systems  
asked by Revering Sumoda 21 votes
answered by David Richerby 32 votes

Can you answer these?

Proof of Randomized Self-Adjusting Binary Search Tree

I developed a randomized self-adjusting binary search tree years ago, which I called a shuffle tree, but was unable to ever have it published because my proofs were rejected (with little explanation). ...

data-structures randomized-algorithms correctness-proof  
asked by Mayur Patel 1 vote

What type of operations are seen the most at the physical disk level — reads or writes? Why?

This question came up in my operating systems class in a section about file system cache and RAID. I'm speculating that the answer is that writes are seen more at the physical disk level because an ...

operating-systems  
asked by donth77 3 votes

Name of a type of code similar to block codes

I've encountered a system where I need to construct a sort of quasi block code: We want to communicate a symbol $s$ from a finite-sized alphabet $\mathcal{S}$ using $N$ segments of information. ...

reference-request information-theory coding-theory encoding-scheme  
asked by enthdegree 3 votes
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