Repeated Stalin Sort
Stalin sort is a "sorting" algorithm where you declare that the list is sorted and remove elements not in order. It's not a proper sorting algorithm as it doesn't preserve the whole list.
Example:
[1,3,2,5,2] This is the list to sort
[1,3,2,5,2] The first two elements are...
Lean golf: m + m = n + n -> m = n code-golf math proof-golf lean
Your job is to prove the statement in the title for natural numbers in Lean theorem prover (Lean 3 + mathlib). Shortest code in bytes wins.
Rules
Your code should provide a named theorem or lemma X such that, when the marked sectio...
Revert Flow Free puzzle
code-golfarray-manipulationgrid
Inspired by Is this Flow Free puzzle trivial? by @Bubbler. Lengthy chunks of this challenge are borrowed from there. This may be one step of a solution for the linked challenge, depending of the strategy.
Background
Flow Free is a series of ...
a + b = b + a
This question is a part of the lean LotM.
Rings are a type of structure that takes the rules of addition and multiplication we are familiar with and abstracts them, so we can reason about them. Rings can be defined in a number of ways. Usually this involves giving a bunch of axiom...
I just had an interview for junior embedded engineer, and they stunned me with next two questions:
by changing on character make this program print '*' 20 times
void main(){
int i, n=20;
for (i=0; i<n; i--)
printf("*");
}
You get numbers from 1 to 1.000.000 in random sequence, int...
Conway's Game of Life is the classic example of cellular automation. The cells form a square grid and each has two states: alive or dead. On each turn, each cell simultaneously updates according to its state and those of its eight neighbours:
A live cell remains alive if it has exactly two or t...
We’d like to introduce version labels (official name and verbiage pending) for answers, a new product feature idea as part of the larger Outdated Answers project. We hope that this feature will help users more easily identify relevant answers that resolve their problems, as well as highlight oppo...
One of my biggest concerns is still that users will tend to misapply the feature. Version tags only provide value if they mark the actual version range where an answer is valid. But if there is a field called "version", I suspect a not insignificant number of people will add the version they used...
Implement this function
code-golf
Your challenge is to implement this function:
$$F(n) = {1! + 2! - 3! + 4! - 5!\dots \pm n!}$$
If n is negative, return -1.
If n is a float, floor n then make the calculation.
Test Cases
6 => 621
-8 => -1
3.1 => -3
-0.6 => -1
20 => 2317323290554617021
There is a "sorting" algorithm often called Stalin Sort, where instead of sorting an array, you just remove any items that are out of order. In this challenge, you'll implement part of a sorting algorithm which recursively sorts the removed items, then merges the arrays to form one (properly sort...
