This one is pretty hard. Definition The 4th derivative of a function f(x) is the derivative taken of this function 4 times at a given point, let's call it x0. This problem is super simple for 1st derivatives since you can just use the limit definition of the derivative and a tiny value for h. It ...

Iteratively delete a list Say I have a ragged list, like: [ [1, 2], [3, [4, 5] ] ] And I want to iterate over each item and delete it one-by-one. However, I don't know the structure of the list. So, I have to iterate over the list, with the following algorithm: Look at the first item...

Requirements For the sake of the challenge let's define a unit: A unit is defined as any point that compose the grid in which the face is drawn (pixels for screen, characters for ASCII art, etc..). The minimal requirements for the face are: A smiley face is composed of a shape that r...

Is it a heapable sequence? code-golf decision-problem data-structures We say a sequence of integers is heapable if there exists a binary max heap, whose nodes are the sequence's elements, such that if \$p\$ is the parent of \$n\$, then the sequence has \$p\$ before \$n\$. Alternatively, a sequenc...

Give f and g that sometimes commute code-golf open-ended-function Write two functions \$f\$ and \$g\$ over the integers, such that: \$f(g(a)) = g(f(a))\$, for infinitely many integers \$a\$, and \$f(g(b)) \ne g(f(b))\$, for infinitely many integers \$b\$. Rules Interpret "function" in the math...

Unicode Clock Plot contrivance You wake up to find that something has gone horribly wrong! Your time machine has horribly malfunctioned and now you are lost sometime between now and October 1991. You check the computer that you keep on the desk to see what time it is but alas the positron interf...

Compute the cophenetic correlation coefficient Meta question at the end. Background The cophenetic correlation coefficient is used in bioinformatic to measure how close the distances of a tree are to the distances of the original distance matrix. It is defined as follows: \${\displaystyle c={\fra...