I wanted to finally reach red (after being stuck at orange for some years now) and I asked myself what should I study. I thought I should review one of the most important things I learned, that helped me go from expert to master very quickly, but then I realized I've never seen people referencing that resource here in codeforces, which seems crazy to me.
The main ideas are presented in a paper titled Pessimal Algorithms and Simplexity Analysis by Andrei Broder and Jorge Stolfi, which is available online for free.
I wanted to present this old paper to codeforces, urge you to read it if you haven't (it's just 5 pages long), and, if you have read it, ask you if you have benefited from these very useful techniques and concepts too (I'm sure you have, it's just that I'm perplexed I haven't seen it mentioned here before).
I'm confident that studying again these concepts will make reaching red easy (and make me a better programmer in general)