kinetic segtree

For me it's the Round-Square Tree data structure. I use it almost every day but not many people know about it.

Implicit Persistent Treap Beats. UUUU

Putting my fist into my mouth

How to mod multiply two large numbers in C++.

bitset

For me it's this

Segment tree, but get this: with lazy propagation

Also bitwise trie (if you consider that more advaned than the segment tree)

math

Binary Search

You know algorithm floyd? Most of people just memorize it without understading and there is a special order of for's ( loops ). But instead of memorizing the correct order you can just write them in random order and copy past it three times in you code it will work correctly!

virtual tree / auxiliary tree (however I like to call it an LCA tree)

Binary search

Let $$$f(x)$$$ be a polynomial with non-negative integer coefficients for which $$$f(10)$$$ is prime. If the coefficients of $$$f(x)$$$ are at most $$$49598666989151226098104244512918$$$, then $$$f(x)$$$ is irreducible.

I hope I will get to use this theorem in a real programming contest one day :(

Stop stressing over so much for EJOI. You don't need to learn anything new. Graph bundling

Lagrange interpolation