Tomorrow, the National Romanian Olympiad will take place. After 4 years of practice, my competitive programming high-school journey will soon reach an end. It was nice joureny filled with ups and downs. It will be my last attempt, so I'll give it my best effort. I'm hoping for a silver medal, or maybe even gold.

Good luck to everyone participating in the olympiad tomorrow! May you fulfill your expectations.

IF anyone wants to try the problems they will published on this site https://kilonova.ro/ after the contest end.

Because the national Olympiad is in less than a month, I want to practice as much as I can, while documenting my progress to keep myself motivated. Join along on this improving journey!

Starting rating 1600 — Finishing rating: ?

day 0: (30 may) I participated in CodeTon8 and solved problems A, B, C1, and C2. Problem D was too difficult; I will attempt to upsolve it in the next few days. The contest was decent, but I encountered many wrong answers on problem C1 because I used a map instead of a vector. Nevertheless, I successfully solved the geometry problem, which was quite good. Performance: 1533 (-10)

Day 1: I reviewed some graph algorithms such as Dijkstra, Bellman-Ford, and bipartite graphs.

Day 2: I participated in the virtual contest for 936 (Div2). I solved problems A, B, and C. My approach to problem C was clean, and I had the right idea for problem D. I implemented it after looking at the editorial, still got 12WA in the process. Performance: 1560

Feel free to give some suggestions for problems or new algorithms to learn, and I might try them in the next few days.

Let me explain! My inspiration came from this problem https://mirror.codeforces.com/contest/1811/problem/E, during contest I wasn't able to solve this DIV3_E, but after seeing the solution I was amazed by how easy and beautiful it was.

Basically you have to convert the number in base 9 and map the corresponding digits.(here is my code: (https://mirror.codeforces.com/contest/1811/submission/201234595)

So of course now it seems relay easy, but at first for me, during contest, it wasn't like that at all.

I am sure you have encountered similar problems and I thought it might be interesting to share them.

Dear Codeforces,

I decided that from June I want to start practicing CP more regularly. So I'll try to solve at least 2 problems daily.

I will select 2 random problems using this website: https://www.dailycodeforces.com/

The first problem is 1400-1500 and the second is 1600-1700 (i will adjust once I am comfortable enough with this rating)

I am sharing all of this with you because I believe that CP is more fun when you do with a friend. So feel free to join regardless your level!

Day 1

https://mirror.codeforces.com/contest/994/problem/B

https://mirror.codeforces.com/problemset/problem/1513/C

Day 2

https://mirror.codeforces.com/problemset/problem/891/A

https://mirror.codeforces.com/problemset/problem/191/B

Day 3

https://mirror.codeforces.com/problemset/problem/1684/C

https://mirror.codeforces.com/problemset/problem/1567/C

Day 4

https://mirror.codeforces.com/problemset/problem/1391/C

https://mirror.codeforces.com/problemset/problem/729/C

TO DO: (if you guys are interested)

1) make a spreadsheet with the problems

2) make short description (only interesting problems) and give my difficulty form (1-5) and topics.

Thanks for reading! I am open to any kind of suggestions.

I want to practice problems from national olympiads and to get a fell about how the problems are around the world I need your help. I found this site https://olympiads.win.tue.nl/ioi/noi/index.html, but some links are broken or unavailable. If you can shortly describe the process of getting to the national (like are there any regionals) and provide a link it would be very helpful.

I will update the blog with your comments.

Hello Codeforces! Because in April I have a lot of free time and I want to improve my CP skills, I will try doing a virtual every day for a month. I don't know if it's the best practice method but I'll still give it a shot. To keep myself motivated I'll update this blog once a week(?). Feel free to join along!

Starting Rating 758 Ending Rating: ?

Day 1: I did ARC 158 where I only solved A

Day 2: CF862 solved A,B quite fast. Unable to solve C with binary search on set(lowerbound). Performance : 1193

Day 3: CF861 (virtual) Solved A,B fast (trey were standard) but got 3WA. I tried C with backtracking but I realized it is too slow. Performance : 1315

Update 1:

Day 4: Today I did CF863 div 3. Like someone mentioned this contest felt like a div 2.25 (at least for me). I managed to solve A,B,C quickly (but still they were a bit tricky) and spent like 1:30 trying for D,E but with no progress. Performance : 1318, Almost reached pupil

Day 5: No contest today :(. I solved 1805C from 862_DIV2 (DAY 2). In the contest I was close : I proved that (b — k) ^ 2 should be < 0. But I didn't realized that we can use upper_bound to look for k since a,b,c are fixed. I enjoyed this problem, it has a nice solution.

Day 6: I tried D from same contest, but I needed to learn All longest path from CPH (competitive programmer handbook). I did that but still got TLE on 8 and I don't know the reason why. My solution seems O(N).

Day 7: I started solving problems from this blog :https://mirror.codeforces.com/blog/entry/114789

Solved:

1519D (1600) I didn't come up with the solution, but when I checked the editorial is was a trivial N^2 dp. Maybe if I spent more time before checking the editorial I could have solved it. Nevertheless a good problem for a beginner with dp.

1324D (1400): Solved using segment tree, probably a huge overkill and the code is not clean (but that is the first solution that came to my mind). I also got lots of WA because I didn't make the segment tree big enough (size).

1808C (1900): (C from Day 3) This problem was surprisingly unintuitive. I'll briefly explain my solution:

1) Eliminate the common prefix.

2) Iterate over the next 2 digits and set the rest of them equal with dg1 and after = dg2

3) Update the best answer that satisfies the constrains

This works because for each pair of digits we only care about the best answer. Since the first digit of a and b now is different we know which is true: either our number is surely < b or surely > a (we discard the other options) so now we can set the rest greedily equal with the max digit (that we set) if we know that x < b or the min digit otherwise.

Conclusion after a week: Don't expect big improvement after working only for a week.

I was solving national OI when I stumbled across this (simple?) problem which I was unable to solve.

"Given N and K find the k-th lexicographically correct parenthesis of length N".

Example:

N = 4 k = 2

()()

Thanks in advance! Hope this question will help somebody else too.