I wish be expert in this contest

I wish be expert in this contest

As a participant, I can't spell BledDest without $$$\textbf{st}$$$.

Good luck everyone! I hope I can climb back to Specialist

I wish problems are in my favour

score distribution?

Hoping for +1.

Ill reach expert tomorrow

Ill reach expert tomorrow

I'm not a magician, but u'll get WA at test 2 in problem B tomorrow

As i participant i would participate

Hoping for positive delta :D

First Edu round in 2025?

Hope to reach 1700!

а в чем разница Educational от простого соревнование?

and what is the difference between Educational and a simple competition?

all the best for everyone,hoping everyone would increase there ratings

I wish be master in this round.

Last contest I become Expert,but this time I will return to the pinnacle!

Last time I become Expert,but this time I will return to the pinnacle!

Pls no GCD again.

Hope you become grandmaster if you pray for Palestine!

SpeedForces scheduled.

Thanks for the non GPTable D. Atleast not by just copy pasting the question. I tried it out by participating unrated.

ShitForces

Problem E is close to this problem: 1686D - Linguistics

I hated E. D was not the best as well. I guess C was the best one ...

How to solve C?

Tests for E are terrible tbh

Why This this code fails for problem B?

How did you all do C? I wasn't able to solve it after trying a lot of times, always failing test case 3,4,5 or TLE

I tried checking all the indexes of 1 and 3 in the given array, and for n number of 2's in between the indices, I added $$$2^n-1$$$ to the answer, making sure to use MOD exponentiation. :(

How to solve E?

1685B - Linguistics

p.s. i didn't know the problem and didn't solve E this time

positive delta plzzzzzzzzzzzzzzzzzzzz

I did not realize C was just dp lol... I did it in such a different convoluted way 306723210

Tutorial: How to solve E

Firstly, solve this problem

https://mirror.codeforces.com/contest/1686/problem/D

Then solve E

Took 66 minutes and 3 WA for A and B each but solved C in 26 minutes first try lmao. I probably should've reread the problem and not spam solutions.

Who is discussing today's contest ??

Shayan ? Aryanc403 ?

problem C already existed: 105444G - Gig Combinatorics jasjajs

problem C already existed hashhas: 105444G - Gig Combinatorics

306742121

C. WTF is wrong with this DP solution why am I getting TLE

Why is my code for B giving MLE? I have following code:

void solve() {
  int n, m;
  cin >> n >> m;
  vector<vector<int>> a(n, vector<int>(m, 0));
 
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      cin >> a[i][j];
    }
  }
  vector<pair<bool, bool>> singleDouble(n * m + 5, {0, 0});
 
  vector<vector<bool>> visited(n, vector<bool>(m, 0));
 
  queue<pair<int, int>> q;
  vector<pair<int, int>> dx{{-1, 0}, {0, -1}, {1, 0}, {0, 1}};
 
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      if (!visited[i][j]) {
        q.push({i, j});
        while (!q.empty()) {
          int ii = q.front().first;
          int jj = q.front().second;
          q.pop();
          singleDouble[a[ii][jj]].first = 1;
          visited[ii][jj] = 1;
          for (auto &p : dx) {
            int x = ii + p.first;
            int y = jj + p.second;
 
            if (x < n && x >= 0 && y < m && y >= 0) {
              if (!visited[x][y]) {
                if (a[x][y] == a[ii][jj]) {
                  // parent[x][y] = parent[ii][jj];
                  singleDouble[a[x][y]].second = 1;
                }
                // singleDouble[a[x][y]].first = 1;
 
                q.push({x, y});
              }
            }
          }
        }
      }
    }
  }
  int solution = 0;
  bool hasTwo = 0;
  for (auto p : singleDouble) {
    if (p.second == 1)
      hasTwo = 1;
    if (p.second == 1) {
      solution += 2;
    } else if (p.first == 1) {
      solution += 1;
    }
  }
 
  if (hasTwo)
    solution -= 2;
  else
    solution -= 1;
 
  cout << solution << endl;
}

Every one of my variable should be around 5e5 * 4 = 2MB? And I have four of such variables(queue, singleDouble, visited, a). So shouldn't this be 10MB? Very less than 256MB limit?

Take a look at my abomination of a solution for D

If you don't want DP for C here is mod inverse(I hope don't get hacked).

Also did anyone felt problem A to be hardest like if the ordering was C D B A then it would be better?

For B, what is the result supposed to be for:

1
2 3
2 2 2 
5 4 4 

:(

Problem A took me 30 minutes to debug because the array is not initialized. I finally solved only 2 problems. Goodbye Specialist.

Thanks, I was 1395 but now I will not be a specialist yet :)

Hurts :")

CAN ANYONE TELL WHY THIS IS FAILING TEST 3

306757323

What is a successful hack test for B?

Thanks a lot for D! It's the best binary search problem I have solved till now!

Problem C is similar to 1955. Count Number of Special Subsequences.

Emmm. E may be a little ad-hoc. I thought it could be a non-greedy problem. But when I found the correct greedy strategy, I had spent $$$70$$$ minutes on E. When I found F is a simple use of Segment Tree Divide and Conquer, I feel very upset!

Could someone explain why my B won't pass? if a color has no strangers, it can be changed to a third color in 1 operation, else it would take 2 operations. So I just count the number of operations required to change all colors to a third color. It would be optimal to change all colors to an existing one. If a 2 operation color exist, it would be optimal to change all colors to that one, else we can change all colors to any arbitrary color. If there is only one color, we don't need any operations. What am I missing?

https://mirror.codeforces.com/contest/2069/submission/306732090

Can E be solved by using flow ?

when will system testing start and by what time will the ratings be updated??

Please make better pretests. Seriously... negative mod is not a very rare or unexpected problem when its a problem about PIE (the brute force is literally summation of all j > i where a_i = 1 and a_j = 3, 2^(count of 2s between i and j) — 1), so some people would keep the PIE by subtracting by prefix frequency of 1s.

This is a standard issue, and while is a dumb error on the participants' part, is a minor mistake and should be penalised with a WA on tc 4 or something, not a FST/hack. How do you fail to catch this? And this isn't a small issue either, By going from the 3000 place to 3500, I was able to find 8 fsts within an hour without even inspecting every single one... i skipped by 5 or 10 randomly sometimes. Such a common mistake should be penalised.

Please do better. Or maybe???? insane idea... add testers to Edu rounds? Like seriously EVERY other division has testers, and they end up with nicer problems (this is not only my opinion there are many in the community who beleive this), I'm sure some people would be willing to test so why not introduce that... Your three person team appears to be incompetent at problemsetting.

Please check why my approach to C gives a MLE

here

I haven't learnt dp, I tried without it

ans should be the summation(2^k_i — 1) where k_i represents no. of 2's between every pair 1,3

Why is carrot not working to predict ratings for this round?

So when can the editorial be published?

When will the ratings be updated?

When will you give the editorial??

i rigistered for rated, but it shows me unrated, why is that happening

Why is it unrated?

I believe this round was rated right? will they update the score or the round became unrated ?

When we will get our rating changes? Is system testing done?

Who can tell me why I was unrated in this contest?

The system test doesn't seem to have started yet. Just stay patient—things will happen when they're supposed to.

will they publish the result? and why its too late?

Auto comment: topic has been updated by awoo (previous revision, new revision, compare).

Not me hitting the refresh button every 10 second for rating change.