How to generate a random sequence (permutation) of a finite sequence.

max_heap: A[0] is the maximum value
min_heap: A[0] is the minimum value
source code: AC/Algorithms/Heap

My simple note on the RSA algorithm.

BIT can be used to compute the prefix sum of an array in $log(n)$ time and takes only $O(n)$ space.

source code

Use matrix and fast pow together can make some problems much easier.

knapsack problem and its variations

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

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.