Question

In a (possibly directed) graph, is there a simple way to find all nodes reachable for a given node?
I've recently started working with MATLAB graphs. In two recent problems, I have graphs which are not known to be connected eve...

9 months ago | 2 answers | 1

2

answers

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Compute the Sisyphus sequence
A recent article in the New York Times featured the Online Encyclopedia of Integer Sequences, founded by Neil J.A. Sloane. One o...

1 year ago

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List primes of the form xy+z
Consider three consecutive integers , , and . When is the number prime? For example, if or , then the results are 17 and 37, ...

1 year ago

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Determine whether a number is a Gaussian prime
A Gaussian prime is a number that cannot be factored. For example, is not a Gaussian prime because it can be factored as the p...

1 year ago

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Express numbers as the sum of a prime, a square, and a cube
While traveling on an interstate highway, I noticed a sign that gave distances to three places. The distances were 3, 8, and 9 m...

1 year ago

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Determine whether a number is a Zeisel number
Do you know what is interesting about the number 1729? That’s right: it’s the third Zeisel number, a number given by , where ...

1 year ago

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Compute the largest number whose prime factors sum to n
This problem deals with a sequence whose tenth term is 36 because the prime factors of 36 (2, 2, 3, 3) sum to 10. The number 32 ...

1 year ago

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List the Moran numbers
The quotient of a Moran number and its digit sum is prime. For example, 117 and 481 are Moran numbers because 117/(1+1+7) is 13 ...

1 year ago

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List the cuban primes
The number 61 is a cuban prime because it is prime and the difference two cubes, 64 and 125. Write a function to list the cuba...

1 year ago

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List the semiprimes
A semiprime number—or a 2-almost prime—is the product of two prime numbers. The numbers and are semiprimes, but and are not....

1 year ago

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Compute the bubble popper fidget spinner sequence
A fidget spinner is a toy made of multiple lobes that pivot on a ball bearing. In some, the lobes hold bubble poppers, or rubber...

1 year ago

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Factor a number into Fermi-Dirac primes
Cody Problem 58018 asked you to list the Fermi-Dirac primes, which are prime powers with exponents that are powers of 2. As note...

1 year ago

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List the Fermi-Dirac primes
The Fermi-Dirac “primes” are prime powers with exponents that are powers of 2. The first nine terms of the sequence are 2, 3, 4,...

1 year ago

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Identify de Polignac numbers
The numbers 125 and 329 can be written as the sum of a prime and a power of 2. For example, , and . The numbers 127 and 331, whi...

1 year ago

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List numbers such that every sum of consecutive positive integers ending in those numbers is composite
The sequence in question in this problem involves numbers such that all sums of consecutive positive integers ending with are ...

1 year ago

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List the two-bit primes
Each year at Christmas, my father-in-law and his partner send me the Puzzle Mania section from the New York Times. This year’s e...

1 year ago

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Solve an equation involving primes and fractions
Write a function to find pairs of primes and satisfying the equation where is an integer. The function should take a numbe...

1 year ago

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List odd twin composites
Twin primes, or prime numbers that differ by 2 (e.g., 17 and 19, 59 and 61, or 191 and 193), are the subject of several Cody pro...

1 year ago

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List the Beatriz numbers
Write a function to find integers less than or equal to an input value that solve the equation . The function gives the sum o...

1 year ago

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List the Euclid numbers
Euclid proved that the number of primes is infinite with the following argument. Suppose the primes form a finite set , , . Comp...

1 year ago

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Create Combination
Motivation: In many problems, we need to create combinations with the function nchoosek. In some cases, however, choices are lim...

1 year ago

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Usage of java.math : N Choose K with unlimited precision
Calculate the binomial coefficient nchoosek with full accuracy. This challenge may use the wonderful word of java.math that allo...

1 year ago

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Get ranking of a combination looking for speed.
I have the numbers pulled without replacement from the set [1 2 3 4 5 6 7 8 9 10 11 12 13]; They are then ordered from least to...

1 year ago

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Get ranking of a combination
I have the numbers pulled without replacement from the set [1 2 3 4 5 6 7 8 9 10 11 12 13]; They are then ordered from least to ...

1 year ago

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Put m balls into n boxes (again)
According to Cody Problem 1516, if I put 3 balls into 2 boxes then 1 1 1 1 1 2 1 2 2 ...

1 year ago

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Put m balls into n boxes
Can you find all the cases where, if I put 3 balls into 2 boxes the case is 1 1 1 1 1 2 1 ...

1 year ago

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Numbered lottery balls into cells
You are running a lottery, and have a number of different balls numbered 1 to N. Your job is to figure out how many different w...

1 year ago

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A (wrong) place for everything, and everything in its (wrong) place
You have an equal number of cups and balls, each labelled from one to N. You randomly place one ball in each cup. Determine th...

1 year ago

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Possible Outcomes of American Roulette
The payout for American roulette can be calculated by: payout = (38/n)-1 where n is the number of squares the bet covers. ...

1 year ago

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NCHOOSEK - Time Optimization
Input V —— Set of all choices, a vector of N, 1 < N < 100 K —— Number of selected choices, a scalar, 0 <= K <= N Output C ——...

1 year ago