TrainOI

Trainer for competitive programming.

Problems are sourced from the public Codeforces problemset. Codeforces is not affiliated with TrainOI.

How It Works

A lightweight recommendation engine selects unsolved Codeforces problems near your rating and biased toward your weakest skills.

Pick Bronze, Silver, Gold, Platinum, or General and start a timed training session.

We pull Codeforces problems in difficulty bands (±200) and target weaker skills first.

Solving a problem helps your skill and rating improve; give up to move on with a small rating loss.

Each higher module includes earlier fundamentals (Bronze topics flow upward). General uses all categories.

Implementation basics, simple data structures, math, strings.

Adds graph fundamentals (search, trees) to Bronze foundations.

Introduces dynamic programming while reinforcing graphs & math.

Adds advanced techniques (FFT, meet-in-the-middle, complex DS).

ELO is calculated with k factors decreasing logarithmically from 20 to 5 depending on your rating.