I've joined Codeforces 4 months ago. The first goal I set for myself is becoming a blue coder. But after I've taken part in some contests I found it's not so easy. I've taken part in 9 contests and my current rating is 1363. In Div.2 contests I can averagely solve 2 problem. But I sometimes haven't got any ideas for problem C! And when I'm analyasing how some of my friends (tzc_wk, dxctrl) became blue, I found that they have one thing in common: they all have the ability to solve Div.2C. So it seems that to become blue I should have the ability to solve Div.2C. But what problems should I do? With what level of difficulty? What kind of algorithm? Greedy, graphs, DP, math or something else? I'm really confused.

The problems you manage to solve in-contest tend to be a step down in difficulty from the hardest problems you solve in practice.

look. try to open, say 250 div2 contest and start solving from there every C problem. 592 — 250 and you have 342 C already solved problems. But first, read this shit

Bad advice. As socketnaut said above solve D-E in practice to solve C in contest.

What helped me come out of Div2 A and B was learning new things.

I learned dfs, bfs, and solved a lot of greedy problems. I learned very frequently used data structures such as segment trees. I solved some good problems on binary search. Learned a bit about primes as well.

I guess this was enough for me to solve Div2 C, and sometimes Div2 D as well.

Obviously, solving good(higher in rating) problems in practice helps.

Read this. https://codeforces.com/blog/entry/69100

Also, there is no easy way to become blue. I do CP about 2 years and still blue

Solve +1500 difficulty problems ( In my opinion ) and start learning more advanced DS and algorithms

But ... But ... why doesn't it seem to be working (at least in your case)?

I analyzed your profile using Codeforces Visualizer and Code Drills it seems you haven't really solved much C problems.

Use this link to solve codeforces C problems sorted by difficulty and trust me you will start seeing improvements after solving about 50 problems, I am also using it and I solve a minimum of 3 div2 C problems every day (sometimes try practicing div2 D problems too).

I have started noticing improvements too, matter of fact I just became 4 stars on codechef and I know it isn't much of an achievement but I'm proud of it :) all thanks to these div2 C problems I solve every day, it's the only form of practice I've been doing for a month now.

Also, try solving A and B as fast as possible during contests, it gives you time to think about the C problem and sometimes it puts you in a good rank already during the contest.

EDIT: Try disabling tags too, it helps.

PS: We can practice together if you don't mind :)Well, it seems that more and more people are able to solve div 2 problem C (in contest) nowadays. So even you can solve problem C in contest, unless you can do it very fast (within first 20 to 30 minutes, that's not likely to get you in a very good rank.

It will at least get you to the rank of specialist, which would still be an improvement for the OP.

D is the new C as no longer we get 5-problemset format contests.

Solve problem D with DP or graphs