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# Vinh Dinh

Last seen: 3 månader ago Active since 2021

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Sophie Germain prime
In number theory, a prime number p is a *Sophie Germain prime* if 2p + 1 is also prime. For example, 23 is a Sophie Germain prim...

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MATLAB Basic: rounding II

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Get the length of a given vector
Given a vector x, the output y should equal the length of x.

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Rotate and display numbered tile
Imagine a square tile with four numbers on it, one on each edge. We will call these edges north, east, south, and west. If th...

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Stuff the Board
You have a stack of tiles to put onto an array-like playing board. Each tile has a number (always an integer), and the board var...

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Scoring for oriented dominoes
Given a list of ordered pairs, and the order they should be placed in a line, find the sum of the absolute values of the differe...

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Find best domino orientation
Given a list of pairs, find the orientation they should be placed in a line, such that the sum of the absolute values of the dif...

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Choose the best fitting dominoes
You will be given a cell array of nx2 matrices. Choose one row from each matrix. These are the ordered pairs that will be plac...

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Find best placement for ordered dominoes (harder)
Given a list of ordered pairs, find the order they should be placed in a line, such that the sum of the absolute values of the d...

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Find perfect placement of non-rotating dominoes (easier)
Given a list of ordered pairs, find the order they should be placed in a line, such that the sum of the absolute values of the d...

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The Goldbach Conjecture
The <http://en.wikipedia.org/wiki/Goldbach's_conjecture Goldbach conjecture> asserts that every even integer greater than 2 can ...

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Circular Primes (based on Project Euler, problem 35)
The number, 197, is called a circular prime because all rotations of the digits: 197, 971, and 719, are themselves prime. The...

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Mersenne Primes vs. All Primes
A Mersenne prime (M) is a prime number of the form M = 2^p - 1, where p is another prime number. <https://www.mathworks.com/matl...

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Find vampire numbers
A <http://en.wikipedia.org/wiki/Vampire_number vampire number> is a number v that is the product of two numbers x and y such th...

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Find the next prime number
Find the next prime number or numbers for given n. For example: n = 1; out = 2; or n = [5 7]; out = [7 11]; ...

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Make a vector of prime numbers
Input(n) - length of vector with prime numbers Output(v) - vector of prime numbers Example: * n=1; v=2 * n=3; v=[2 3 5...

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Largest Twin Primes
<http://en.wikipedia.org/wiki/Twin_prime Twin primes> are primes p1, p2 = p1 + 2 such that both p1 and p2 are prime numbers. Giv...

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Mersenne Primes
A Mersenne prime is a prime number of the form M = 2^p - 1, where p is another prime number. For example, 31 is a Mersenne prim...

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Find nearest prime number less than input number
Find nearest prime number less than input number. For example: if the input number is 125, then the nearest prime number whi...

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Is this triangle right-angled?
Given any three positive numbers a, b, c, return true if the triangle with sides a, b and c is right-angled. Otherwise, return f...

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Smith numbers
Return true if the input is a Smith number in base ten. Otherwise, return false. Read about Smith numbers at <http://en.wikipedi...

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Prime factor digits
Consider the following number system. Calculate the prime factorization for each number n, then represent the prime factors in a...

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Numbers with prime factors 2, 3 and 5.
Make a function which takes one positive integer n and returns a matrix with the numbers of the form (2^i)*(3^j)*(5^k) which are...

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Generalised Hamming Number
Inspired by Project Euler n°204 and Problem 1308 by James A generalised Hamming number of type n, has no prime factor larger ...

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Factorize THIS, buddy
List the prime factors for the input number, in decreasing order. List each factor only once, even if the factorization includes...

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Get all prime factors
List the prime factors for the input number, in decreasing order. List each factor. If the prime factor occurs twice, list it as...

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Proper Factors
Generate the proper factors of input integer x and return them in ascending order. For more information on proper factors, refer...

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Multiples of a Number in a Given Range
Given an integer factor _f_ and a range defined by _xlow_ and _xhigh_ inclusive, return a vector of the multiples of _f_ that fa...

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Find max prime number
Given integer number n. Find the max prime number (mpn) that smaller than or equal to n. Example: n = 10 --> mpn = 7