A method for preliminarily learning difficulty concepts/data structures/algorithms and being able to put them to use very quickly... within minutes!

In short: blindly copypasting code is okay, most of the time.

Stuff I said would be in the description:
AtCoder Library: https://codeforces.com/blog/entry/82400
cpalgorithms: https://cpalgorithms.com/
kactl: https://github.com/kthcompetitivepr...
Benq's library: https://github.com/bqi343/USACO
My library: https://github.com/galencolin/cptemp...
A cool online judge to test library code: https://judge.yosupo.jp/

Some timestamps:
Intro/overview 00:00
Black box description/examples 01:00
How to use it 04:17
Advantages 07:06
My personal examples 09:00
Practicality/useful libraries 11:27
Final remarks 13:07