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# David

Active since 2018

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Solitaire Cipher
Implement the <http://en.wikipedia.org/wiki/Solitaire_(cipher) solitaire cipher>. Since this is from Wikipedia, I am capturin...

nästan 5 år ago

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How long is the longest prime diagonal?
Stanislaw Ulam once observed that if the counting numbers are <http://en.wikipedia.org/wiki/Ulam_spiral arranged in a spiral>, t...

nästan 5 år ago

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Make a run-length companion vector
Given a vector x, return a vector r that indicates the run length of any value in x. Each element in r shows how many times the ...

nästan 5 år ago

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How many trades represent all the profit?
Given a list of results from trades made: [1 3 -4 2 -1 2 3] We can add them up to see this series of trades made a profit ...

nästan 5 år ago

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Flag largest magnitude swings as they occur
You have a phenomenon that produces strictly positive or negative results. delta = [1 -3 4 2 -1 6 -2 -7]; Marching thr...

nästan 5 år ago

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Given a window, how many subsets of a vector sum positive
Given a vector: [1 0 -1 3 2 -3 1] and a window of 2, A sliding window would find: 1 + 0 = 1 0 - 1 = -1 ...

nästan 5 år ago

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Find a subset that divides the vector into equal halves
Given a vector x, return the indices to elements that will sum to exactly half of the sum of all elements. Example: Inpu...

nästan 5 år ago

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Spot the outlier
All points except for one lie on a line. Which one is the outlier? Example: You are given a list of x-y pairs in a column ...

nästan 5 år ago

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Implement simple rotation cypher
If given a letter from the set: [abc...xyz] and a shift, implement a shift cypher. Example: 'abc' with a shi...

nästan 5 år ago

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Find the biggest empty box
You are given a matrix that contains only ones and zeros. Think of the ones as columns in an otherwise empty floor plan. You wan...

nästan 5 år ago