2-butterfly derangement â€” The hallmark of the Cooley-Tukey algorithm for Fast Fourier Transform is the butterfly network, which helps reduce $O(n^2)$ computations to $O(n log n)$. Butterflies are

Maximum weighted independent set - connected component â€” Given a weighted connected component, what is the weight of the maximum independent set, and how many different sets have this weight? A Petersen graph

Maximum weighted independent set - singletons and forest â€” Gus wants to open franchises of his restaurant, Los Pollos Hermanos, along Central Avenue. There are $n$ possible locations for franchises, where location i is

Rational numbers in decimal â€” In decimal representation, rational numbers either terminate after a finite number of digits or produce a repeating sequence. Conversely, any repeating decimal can be converted