Computational complexity, a part of theoretical computer science.

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Relation of encryption to P, NP, and NP-Complete

After watching a Harvard Lecture regarding the understanding of P, NP, and NP-Complete,they also talk about our encryption algorithms being cracked or useless once we solve the mathematics side of it? ...
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Show L1 is in P, given that L2 is in P and L1 <=p L2

Given L1 and L2 are languages over alphabet Z. Also given that L1 <=p (polynomial time computable) L2 and L2 in P. What is the best way to show that L1 is in P (through definitions of class P and ...
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Basic questions about descriptive complexity

I'm trying to learn descriptive complexity, and I'm having trouble on a basic level wrapping my head around what it means for a logical formula to define a computational language. I've tried and ...
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How to prove this polynomial expression.

Let the polynomial be in $f$ be a map from $\Bbb{Z}_2^k \to \Bbb{Z}_2$, defined by $f = 1 + \sum_{i=1}^k x_i + \sum_{i\neq j; i,j = 1}^k x_i x_j + \dots + x_1 x_2 \cdots x_k$ Then I want to show ...
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Properties of smallest expressions for polynomials, and potential proof.

See here for an intro. Smallest expressions for polynomials is analogous to smallest grammars for strings. Let $R = \Bbb{Z}_p[x_1, \dots, x_k]$. My goal is to prove that for any $\ \ h(k,p) = \max ...
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Linear search average-case complexity?

I am trying to find the average case complexity of the linear search. I know the answer is O(n), but is this correct: The first element has probability $1/n$ and requires 1 comparison; the second ...
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Is there any oracle A s.t. NP$^A$ $\neq$ EXP$^A$

I think the answer is yes because we do not know whether NP = EXP. But i couldn't find one.
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I want to know an estimate of $a_{i, j}$

Let $$ a_{ij} = \begin{cases} -1, & \text{if $i = -1$ and $j = -1$} \\ 1, & \text{if $i = -1$ and $j \ne -1$} \\ 1, & \text{if $i \ne -1$ and $j = -1$} \\ a_{i-1, j-1} + ...
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23 views

Are there known patterns among minimal expressions?

Let $R = F[z_1, z_2, \dots]$ be the finite-degree polynomials in a countable number of variables. Let $\mathcal{E}(R)$ be the set of all expressions of polynomials. Note that there could be an ...
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Computational complexity of expanding a MacLaurin/Taylor Series

What methods exist to computationally determine the first $k$ coefficients of a function (possibly polynomial or rational polynomial function)? How do Mathematica/MatLab/Maple/etc. solve this ...
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How do you reckon Big-O analysis with infinite problem sets?

Let $f : X \to Y$ be a problem, for instance, $f: \Bbb{Z} \to $ a factor. Given input measure $n = |x|$, then our problem is $O(g)$ if there exists an algorithm running on a standard machine, and an ...
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My notes on $\Bbb{Z}/p\Bbb{Z}$-theoretic computational complexity

(Question at the very bottom) Def 1. Let $F = \Bbb{Z}_p$ be a finite field. Then an $F^k$-machine is a machine with $k$ input / output memory slots. All computations are done in the field $F$ and ...
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How do you define computational complexity abstractly?

Let the problem we're studying be $f : X \to Y$. Say, I don't know what I want to define time-complexity with respect to, I just know I have a map $|\cdot| : X \to \Bbb{R}$, such that $|\cdot| \geq ...
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Not every polynomial in $\Bbb{Z}_p[x]$ can be factored, but can you do next best?

If $f \in R = \Bbb{Z}_p[x]$ is irreducible or doesn't have many factors then it could be hard to compute? Possibly, I'm not saying, but... any way, what if $f = h - g$ where $h, g$ are heavily ...
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Do there exist polynomials not computable in polynomial time?

Motivation: Computing a problem in $k$ memory slots Do there exist polynomials in $R = \Bbb{Z}_p[z_1, \dots, z_k]$ that can't be computed in time polynomial in $k,p$? Thanks... Good luck! Edit. I ...
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Any problem computable in $k$ memory slots can be computed with polynomials.

Let our memory slots be represented by elements of $\Bbb{Z}_p$ for a prime $p$. $k$ memory slots would be $k$ copies of the ring: $R = (\Bbb{Z}_p)^k$. Suppose that for a problem $f : X \to Y$, ...
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circuits complexity

I ran into this claim and I dont really understand why it is true ( and I need to use it for proving other things) Every function from $(0, 1)^n$ to $(0, 1)$ is computable by a $2^n10n$-sized ...
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Is there a way to compute if(i < j) k := (a + b)c with polynomials over $\Bbb{Z}_p$?

Let $p$ be a prime and let all variables be in $\Bbb{Z}_p$. Then you can write the result of if(i > 0) k = (a + b)c; (C code) as a polynomial $k := ...
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Are these computational models equivalent?

Let $f : X \to Y$ be a problem that you want to compute. Say we have an $O(1)$-computable maps, $\phi, \psi$, such that $X \xrightarrow{\phi} (\Bbb{Z}_n)^k \xrightarrow{\psi} Y$. After all, ...
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Existence of a det. poly-time algo for problem $f: X \to Y$.

$f : X \to Y$ is a deterministic polynomial-time algorithm for problem inputs $x \in X$ and problem outputs $f(x) = y \in Y \iff $there exists a polynomial $P_f \in \Bbb{Z}[x_1]$ such that $C\cdot ...
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How do you find a minimum of a function with these tools?

Let's say I can define a group $G$ acting on a set of combinatorial objects $X$ and I have a function $f: X \to \Bbb{N}$ that I want to find a minimum of in $X$. Is there a polynomial time ...
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Can cuts of size 2 be detected in linear time in an undirected, unweighted graph?

I'm having trouble finding any literature on the specific subject of 2-edge cut detection. It's not hard to come up with an algorithm that finds all 2-edge cuts in quadratic time, but it's not clear ...
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How to determine sub-exponential time growth?

I'm a little bit confused of sub-exponential time growth; consider the definition from Hoffstein's book An Introduction to Mathematical Cryptography: Given input of $k$ bits, then if an algorithm ...
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Application of Combinatorics, Logic and computability theory in physical science: Tiling of Wang Tile with proportionality

The original problem of Domino Tiling and Wang Tile has great theoretical interest on computability theory... However, the great emerging problem on application of Wang Tile in material science and ...
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Complexity of finding extremal rays

Suppose that $\{L_i\}$ is a collection of $k$ linear forms on $\mathbf R^n$. Let $$C=\{x \in \mathbf R^n : L_i \cdot x \geq 0 \text { for all } i \}$$ be the closed convex cone defined by the ...
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If $P=NP$, prove that $L' \in NP$

I think I'm overthinking this problem and need some hints in the right direction. The goal of this question is to show that if $P=NP$ then for every language $L \in NP$ via a polynomial time verifier ...
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34 views

Order functions by speed of their asymptotic growths

We are given list of functions. Task is to sort it by the speed of their asumptotic growth in ascending order. Yes, it's a homework. I already spent some solid amount of time calculating limits. I ...
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Proof of theorem about connection between nondeterministic and deterministic Turing machines complexity classes

I need source for proof of this theorem: Every $T(n)$ time nondeterministic Turing machine has an equivalent $2^{O(T(n))}$ deterministic Turing machine. I have book by Michel Sipser, ...
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Prove that THEOREMS is NP-complete

I have an essay where I shall explain polynomial time reductions, NP definitions and give an "non-strict" proof that THEOREMS is NP-complete. THEOREMS is the problem of providing mathematical proofs ...
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What does psuedo-polynomial algorithm for subset sum problem mean?

Help me out here - just trying to better understand what 'psuedo-polynomial' means... If the input to an NP-Complete problem is 100 items(ie n=100), and the 'target' is the actual value '100'(t=100): ...
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Prove 2-HamiltonianCycle $\in \textbf{NP}$

Just want to verify that I have the right idea here with this hamiltonian cycle question. $HC$ = $\{\langle G \rangle$ | $G=(V,E)$ is an undirected graph such that there is a simple cycle (no vertex ...
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Implication of P =NP on video games?

I was wondering if NP problems were actually solvable in P time, then what will be the impact on Video Games, if any ?
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Is $\log^* (n+1)^{n+2} \in O(\log^* n)$?

I would like to know if $\log^* (n+1)^{n+2} \in O(\log^* n)$, where $\log^*$ is the iterated logarithm. I tried doing: $ \log^* (n+1)^{n+2} =\\ \log^{*}(\log(n+1)^{n+2})-1 =\\ \log^{*}((n+2) \cdot ...
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Examples of functions which grow faster than their computational complexity.

A good example of this would be the function $f$ defined as follows, $f(n) = (10^n-1)$. While in this form it's equation is exponential, it is easy to note that $$f(n) = 99...9 \,(n \text{ times}).$$ ...
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Decidability of normal modal logics

Let's say we have systems of modal logic defined as smallest sets containing propositional tautologies, all instances of schema $\square F \to (\square(F \to G) \to \square G)$ all instances of ...
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exponential time complexity

given that: $f(n) = a^n$ and $g(n) = b^n$ where, a,b are positive integers and n is a positive real number does there exist some $f(n) \notin \mathcal{O}g(n)$? ie. $f(n) \leq c_1 \cdot g(n)$ is ...
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A confusion about RP class of problems

I have some notes which introduces the quantifier $\exists^+x$ and interprets it as "the overwhelming majority of $x$". Then, it defines RP (Randomized Polynomial) as: $$ L\in RP\Leftrightarrow ...
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Prove that div(x,y) is primitive recursive (integer division

Prove that div(x,y) is primitive recursive (integer division). I tried thinking about it, I just don't know how to write it formally. it is kinda obvious that I should subtract y from x several times ...
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Why one defines the proper complexity functions?

Definition: A proper complexity function is a function $f$ mapping a natural number to a natural number such that: $f$ is nondecreasing There exists a $k$-string Turing machine $M$ such that on any ...
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Minimizing Height of a Table

This optimization question popped into my mind while working with latex tables: Suppose we have a table with $m$ rows and $n$ columns, and for each $1\le i\le m,1\le j\le n$ we are given $T(i,j)$ ...
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What is the Big O complexity of this equation?

$$\frac{n+1}{2}(\log_2(n-1))+\frac{n+1}{2}-\log_2(1)-\log_2(3)-\dots-\log_2(n)$$ What is the Big O complexity of this equation? My initial guess is $n \log(n)$ But after a calculation, I ...
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The complexity of counting solutions to $x_1 + \dots + x_m = N$ in non-negative integers under constraints

Consider the equation $$x_1 + \dots + x_m = N$$ where $x_1,\dots,x_m \ge 0$ and under the additional constraints $x_k \le a_k$ for $k=1,2,\dots,m$. I'm interested in knowing whether the number of ...
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Why $17T(n/16) + n \log n$ satisfies the case 2 of the Master Theorem?

Using the Master Theorem, we have that $17T(n/16) + n \log n$ is $\theta(n^{log_{16}17} log^2 n)$ My question is, why $n \log n = \theta(n^{\log_{16}17} \log^1 n)$, being $\log_{16}17$ approximately ...
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Complexity Multiplication Matrix-Vector in binary

I'm calculating the complexity of certain algorithm and I need know What's the complexity of the best algorithm, without parallel, to calculate the matrix vector multiplication over GF(2)?. The ...
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How to convert a subgraph isomorphism problem to subset sum problem

Let's say you want to solve a subgraph isomorphism problem using a subset sum solver. What would be the right steps to convert SGI to SS?
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Switching edges and vertices

I am attempting to convert the problem of finding an edge dominating set into a dominating set. I need a way to change the edges of a graph to the vertices and the vertices of a graph to the edges, ...
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Growth rate of $n^{\sin n}$

Is there a way of comparing the growth of functions $ f(n) = n ^ {\sin(n)} $ and $ g(n) = n ^ {1/2} $ in terms of $ O, o, \Omega, \omega, \Theta $ ? Periodically, $ f(n) $ keeps going above and ...
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Lowering the start indexes in sums

I'm implementing a CYK algorithm in my software and I've found a pseudo-code on Wikipedia. Here's its complexity(modified version for special use, which doesn't go from ...
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What is the complexity of computing some problems related to real analysis

I was thinking. I do not know whether my question has any sense. I want to know is there any way to compute analytically or explicitly some of the problems give below. What is the complexity of ...
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problem about computational complexity

Exercise: Prove that the computational complexity of the binomial coefficient \begin{equation*} \binom{m}{n} \end{equation*} is O($m^{2}$$\log^{2}n$). using the fact that the computanional ...