Beginner
[Redcoder’s Guide to Improving Competitive Pro & AtCoder Beginner’s Edition: Let’s Start Competing#競技プログラミング - Qiita
Intermediate
Redcoder’s Guide to Improving Competitive Pro & AtCoder [Intermediate Edition: Aim to Be a Light Blue Coder!] 】 競技プログラミング - Qiita
Expert
Despite this fact, only three things are needed for being rating 1400.
⚫ You can write straight-forward simulation fast. (within 5-10 minutes)
⚫ You can write brute force fast. (within 5-10 minutes)
⚫ You can divide the problem into some cases in your brain or in your paper. (e.g. N=2, N=3, or N>=4)
rating less than 1250 increases rating. On average, if you can do three things above, your rating will reach 1400.
1000 - 1400
Problems B, C
Problems B
- you can learn how to write simulation and brute force faster.
Problems C
- you can learn how to consider the solution and effective way to use paper (or notebook) to think solution.
If i can’t solve problem, and how long i should wait before looking up the solution?
- if you cannot reach the solution, you should read editorials after 15 minutes thinking if problem-B, and 30 minutes thinking if problem-C,
If i solve problem :
- Even if you solve a problem, until you get used to code faster, there may be something to learn if you look some source codes written by high-rated coders, So, I recommend to look some sample source coders.
Problem C
- When you solve problem C, I recommend you to use paper to consider.
using whiteboard instead of paper is good for some reason?
This method is proven and test, should work in general
1400 - 1900
Major Algorithms
Brute Force DP DFS BFS DIjkstra Binary Indexed Tree nCr, nPr Mod Inverse Bitmasks Binary Search
maybe segment tree.
You can code faster (For example, 5 minutes for R1100 problems, 10 minutes for R1400 problems) Fast coding is very important for Codeforces because generally, if there is a wide gap of difficulty in a contest, fast coding affects rating very much.
How to practice ?
If you are not good at fast-coding and fast-debugging
- solve AtCoder problems.
Problem - C Problem - D
solve them with in 10 minutes.
problem - D in 20 minutes.
than you are DIV1 in fastcoding.
if you are not good at solving more than R1400 in Codefrorces.
you should learn some algorithms above and typically problems in Codeforces.
DP - solve DP tagged problems in Codeforces.
1900 - 2200
To be rating 2200, skills as follows are needed:
You know and can use 10 algorithms which I stated in pp.11 and segment trees (including lazy propagations)
You can solve problems very fast: For example, 5 mins for R1100, 10 mins for R1500, 15 mins for R1800, 40 mins for R2000.
You have decent skills for mathematical-thinking or considering problems
Strong mental which can think about the solution more than 1 hours, and don’t give up even if you are below average in Div1 in the middle of the contest
2200 - 2400
To be rating 2400, skills as follows are needed: ⚫ You should have skills that stated in previous section (rating 2200) ⚫ You should solve difficult problems which are only solved by less than 100 people in Div1 contests
Practice Mental
make a routine that you will do juts before the contest, it directly leads to the concentration during the contest.
don’t care about rating during contest
Don’t care about mistakes. Mistakes are also a good chance to learn, how many mistakes did you made and reviewed
Be careful: do not have too much pressure in contests