my openssl cheatsheet.

HMAC-based KDF(key derivation function)

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

How to select k out of N objects.

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

I used to think deploying my blog with github actions is unnecessary, but now… (真香)
Deploying with github actions is so much faster.

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