Most of the 1500-1800 rated CF problems are constructive. That's why I want to start doing AtCoder regularly. Because someone told me that, in every ABC contest, I will find at least one 1500-1800 CF rated problem which I have to solve using DP / Graphs / Any Algo + DS. Is it true?

Official problem and code link : https://codeforces.com/blog/entry/91195

in the solution of problem B (1526B — I Hate 1111), the author only run the loop for 20 times, how it is guaranteed that the answer will be found within 20 iterations?

because if x is too large, like 10e8, after 20 iterations it will still remain tense to 1e8

please help me to understand this

i am taking about this loop :

rep(x,0,20){
       if (n%11==0){
         cout<<"YES"<<endl;
         goto done;
       }

       n-=111;
       if (n<0) break;
    }

I am so confused about how ratings change nowadays. Look at the two accounts below :

Specialist guy : profile Before doing div2 798, his rating was 1458, he ranked 2027th, his ratings become 1459 (got +1).

Expert guy : profile Before doing div2 798, his rating was 1616, he ranked 2014th, his ratings become 1617 (got +1).

Now I am thinking, how this 2 people got the same rating change? Their ranks are similar but one is 1400+ rated and another is 1600+ rated.

The thing I found out is that to solve any dp problem, I just need to find the recurrence relation, nothing else. How can I build my brain to be strong enough to find any dp relation? Any blog or video or advice for that, please?

I am not good at dp problems, so i want to solve a lots of dp problems. But in cf, when i use tag DP, there comes problem which can be solved by greedy/binary search/others 75% of time. That's demotivated me and i see no improvement on dp.

I know about atcoder & cses dp set, i am solving those. But i want to solve cf/cc like dp problems, so where i will find those? Basically i need cf like dp problems where the solution is only and only dp based, can you suggest any?

In problem F, the rotation of string will cost o(n^2) time. it's ok for this problem. But I want to know is there any o(n) approach to do this work?

In last contest, i reached specialist. It took around 2 years for me to get there. But I want to reach expert with in next 6 months.

I can solve 1500 rated problems with 1 hour. I have good hands on basic ds & algos & stl. Also I can solve graph problems <=1800 rated, but I can not solve dp problems.

Now which topics i should learn? What should be my way of practicing? Till which problem i should solve in contest to reach 1600? If you are a Expert, please suggest me that helped you to reach Expert from Specialist.

Click...Which extension it is? When i can see my performance level?

recently i am seeing lots of graphs problem in div 2 C & D. so i am planning to solve graph problems in range of rating 1500-1800. which graph algorithms i need to learn to solve this rated range problems?