39 questions linked to/from Tips for golfing in APL
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### An abundance of integers!

An Abundant number is any number where the sum of its proper divisors is greater than the original number. For example, the proper divisors of 12 are: ...
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### Random Capitalization

The Task Your task is to create a program or a function that, given an input, outputs the input text with random letters capitalized, while keeping already capitalized letters capitalized. Every ...
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### Create an "H" from smaller "H"s

Challenge Create a function or program that, when given an integer size, does the following: If size is equal to 1, output ...
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### Is this a Permutation of 1..n

Input a non-empty array with $n$ positive integers. Test if the input array contains every integer in $1\cdots n$. In case you prefer 0-indexed numbers, you may choose to input an array of non-...
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### Let's golf a BIBABOBU decoder

While I was traveling in the future, I noticed a funny game among kids circa 2275. When they don't want their great-great-great-great-grand parents to understand what they're saying, they use the ...
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### Are All the Items the Same?

Given a list of non-negative integers, return whether or not that list is all the same number. Rules Input and output can be taken/given in any reasonable and convenient format Truthy/Falsey values ...
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### Sum square difference

The sum of the squares of the first ten natural numbers is, $1^2 + 2^2 + \dots + 10^2 = 385$ The square of the sum of the first ten natural numbers is, $(1 + 2 + ... + 10)^2 = 55^2 = 3025$ ...
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### Rotation summation

Take a square matrix containing positive integers as input, and calculate the "rotated sum" of the matrix. Rotated sum: Take the sum of the original matrix and the same matrix rotated 90, 180 and ...
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### The max() is not enough

Intro A friend posed this question today in a slightly different way - "Can a single [Python] command determine the largest of some integers AND that they aren't equal?". While we didn't find a way ...
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### "-rot" transform

Background -rot transform (read as "minus-rot transform") is a sequence transformation I just invented. This transform is done by viewing the sequence as a stack in Forth or Factor (first ...
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### Print the sequence

21, 21, 23, 20, 5, 25, 31, 24, ? Inspired by this Puzzle, given an integer $n>0$ , print out the following sequence until you reach a non-Integer (spoilered, in case you want to solve the puzzle ...
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### Find the nearest greater number

The task Given any array of integers, e.g.: [-1,476,578,27,0,1,-1,1,2] and an index of that array (this example uses 0 based indexing, though you can use 1 based ...
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### Pendulum Encoding

Given a string as an input (which can be any acceptable/convenient format in your language), implement pendulum encoding. The test cases are split into individual items (which aren't quoted) for a ...
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### Pythagorean triples given the hypotenuse

Definition (from Wikipedia) A Pythagorean triple consists of three positive integers a, b, and c, such that a² + b² = c². The typical example of a Pythagorean triple is (3,4,5): 3² + 4² = 9 + 16 = 25 ...
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