Description from wiki: a disjoint-set data structure, also called a union–find data structure or merge–find set, is a data structure that stores a collection of disjoint (non-overlapping) sets

you can easily solve leetcode: 547. Number of Provinces w/ UF.
get UF template at github/sky-bro/AC/Algorithms/Union Find

Easily compile and use multiple glibc on a single machine.

A de Bruijn sequence of order n on a size-k alphabet A is a cyclic sequence in which every possible length-n string on A occurs exactly once as a substring.

For a de Bruijn sequence of order n on a size-k alphabet $A$, we denote it by $B(k, n)$

A segment tree is a binary tree where each node represents an interval. Each node stores some property of its corresponding interval: like the maximum/minimum num, the sum of that interval.