As a tester, orz Error_Yuan! (Yuan shen!)

Not as a tester, I'm not a tester.

test

as tester. awesome problems — hope everyone gets a positive delta!

As a tester, I think these questions are really great and I highly recommend trying to solve them.

as a tester,I tested.

As a tester, I am a tester.

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

As a tester, it’s my first time testing !!

As a tester,

As a tester, this is an auto comment.

As a tester, I murdered 1 problem and solved 0 problems.

As a tester, o_o ,retset a sA

As an author,there was an Auto comment.

Looks like it would be a speedforces round

wow, 5 contests in a week

As a participant, I will participate in this contest

Oh wow, Baozii is actually cursed with testing all rounds.

The only one he didn't test in all of these was Global Round

Hoping to cross 1800 today! Also rooting for the first LGM of my country, Dominater069

Authors, please check RIGHT NOW that AI doesn't solve the problems from this round... Don't want to repeat the experience from the previous round

Good luck for everyone!

As a participant, I wish to reach CM :)

Hope to not get negative delta :)

Good luck to everyone!

Target : atleast 3 questions in 1 hour

Thanks to you

Hoping to reach specialist this round :)

Very excited

If this contest helps me to cross 1000 mark or get low

can't submit.. stuck on verifying you are a human screen for few minutes now :(

Exposing New Cheating Techniques in Codeforces Contests:

• During a recent Codeforces contest, I discovered new cheating methods being employed, which I believe should be publicly exposed to protect the integrity of the community. One of the individuals involved is _ironman_3000, who submitted solutions in multiple programming languages. The submissions appear to be AI-generated, and he spread his solutions across various languages, such as Rust, Node.js, and others, likely to evade plagiarism detection.

• Another individual, AnuragYADAV_10, from Kanpur, India, is also part of this group. Anurag is a student of Aslaan_Khan, who has previously been exposed by the community for similar misconduct. This group of cheaters not only uses AI to generate solutions but also harms the community by spreading solutions in different languages to bypass plagiarism detection systems.

• AnuragYADAV_10 submitted his solutions in multiple languages, including Rust, C++, Python, and Kotlin, seemingly to avoid detection. However, he failed to realize that the Codeforces community itself serves as an effective plagiarism detector. His submission behavior is highly suspicious: fast solution submissions, unusually high rankings, and a history of skipping problems, all point to dishonest practices.

• It’s also worth noting that aslaan001's account has been disabled due to misconduct, and his partner com_gaurav_dev has faced similar consequences. These individuals are part of a group known as the ALGO CLUB on Telegram, where they spread solutions and later convert them into different languages, disrupting the community's fair play.

• For further context, here are the LinkedIn profiles of the individuals involved:

  • Aslaan Khan
  • Gaurav Yadav
  • Anurag Yadav

so small d2 score

vary goods problems i solved A-B-C but C in my mind hahah

C and D1 should have been a little harder. Especially D1.

Very nice problem set

what was the idea for d2?

Thanks author for stupid guessForces round and the -100 delta! Much appreciated <3

Don't know why but B felt too tough!

There was a very similar problem to D1 recently , not sure ( maybe even 2 months back ) . It was div-3 E or F problem I think. If someone finds it please share.

I skipped up-solving it then , could not solve it now either in contest :( . (can't seem to find the older problem now)

Amazing questions!!! Great Comp!!!

If I only managed to program E in time :(

Solved E with segment tree + treap + wavelet tree, loved it!

339769904

can someone explain me the problem with my code and share there approach on C- 339784912

D2 hints please, i can't get through the last example

For D1 my code was

#include <bits/stdc++.h>
using namespace std;
#define ll long long

string ones_complement(unsigned int n) {
    if (n == 0) return "1";
    string s;
    while (n > 0) {
        s += (n % 2 == 0) ? '0' : '1';
        n /= 2;
    }
    reverse(s.begin(), s.end());
    string t;
    for (char c : s) t += (c == '0') ? '1' : '0';
    return t;
}

int bin_to_int(const string &s) {
    int res = 0;
    for (char c : s) res = (res << 1) | (c - '0');
    return res;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int t;
    cin >> t;
    while (t--) {
        int l, r;
        cin >> l >> r;
        
        int n = r - l + 1;
        vector<int> B(n), A(n, -1);
        vector<bool> used(n, false);
        for (int i = 0; i < n; i++) B[i] = l + i;
        for (int i = n - 1; i >= 0; i--) {
            if (used[i]) continue;
            int x = B[i];
            int y = bin_to_int(ones_complement(x));
            if (y < l || y > r) y = x;
            int idx = y - l;
            if (!used[i] && !used[idx]) {
                A[i] = y;
                A[idx] = x;
                used[i] = used[idx] = true;
            }
        }

        long long sum = 0;
        for (int i = 0; i < n; i++) sum += (A[i] | B[i]);
        cout << sum << "\n";
        for (int x : A) cout << x << " ";
        cout << "\n";
    }
    return 0;
}

Can you guys tell me what I am missing my approach was to calculate 1's complement from end and then pair it with their 1's complement. But I am getting wrong ans.

Cool problems! I wonder what D2 solution is

greedy bitwise constructive... i hate cf brainrot so much :/

for problem C, in what testcase does this approach for building the permutation fail:

for all i where s[i] == '1': make p[i] = i + 1

for every subsegment of the permutation where s[i..j] == '0', just set s[i] = i + 1, but in the reverse order in that particular subsegment.

reason: because to make an element stable, we need all elements smaller than it to be only on the left, and larger than it only on the right. if we encounter any subsegment of 0's with length only 1, then it isn't reversible, hence no suitable permutation is possible.