Is there a way to become a tester if there is no communication with codeforces admins?

My first unrated round.

i hope to be specialist after this round ..

It may be a rare 8-problems div 3 round!

OH MY GOD! I can't wait for this div 3 contest! I heckin' love div 3 contests!

As a contestant, I hope the time complexity of me becoming an expert is $$$O(1)$$$.

Will a non-trusted participant be rated? New one here can not be trusted.

Just failed School's selection round for NOI.

This is one of most awaited contest for me , a week without contest on codeforces is hard :( .

I hope I can become blue after this round.

honestly, many of us was waiting for this round, thanks

Very nice! Looking forward to my first rated round

I wish that i become Specialist after this round. Upvote for best wishes. Thanks and Good luck to all.

A round after more than a week. Wish ya'll the best of luck.

Always better to participate in contest instead chatting with gf. Hahaha

Will this round be easier than the last Div.3 contest?

I am on a streak lately, I became 5* on Codechef few days back and qualified for hackercup T-shirt too, I hope my streak continues!

Wish Me Luck!

UPD: Didn't do very good but since I avoided negative delta so I think the streak is still on.

Loved the gradual increase in difficulty in the last contest conducted by +doreshnikov , hope to see a simillar round today!

There is too much of a difficulty gap b/w A and B !! B is not at all a regular Div.3 B problem.

implementationforces

Sorry to bother folks who are participating in today's round, but today's round requires a serious plag check, problem B had a sudden surge in submissions from 3K to 7K in just 5 minutes. Like seriously? I don't think B was an easy one to solve for most folks below the 1300 rating (I got it right after like 5-6 attempts).

While Polycarp is on vacation Casimir is taking over.

Today's round had nice problems (especially F and G). Thanks to MikeMirzayanov for amazing m2.codeforces.com platform (I had connection problems and the lightweight version was very useful). :D

Enjoyed this round. Especially E2.

Holly… Amazing div. 3 round! Btw. anyone knows why cf-predictor is down?

How to solve E2 ?

Is there a way faster than nlogn for E2? I was so happy when i came up with a multiset, but it still TLE

Loved the contest, The Problem D on this contest is similar to a previous Div 3 round D problem.

Link to the similar problem : https://codeforces.net/contest/1506/problem/D

I request everyone , who read the problem D or solved it to go through it also once.

The concept required to solve both the problems are similar.

It is such a nice question on the application of Heaps(Priority Queues).

Good round. BTW, how to solve G?

Did I just participate in a div-2 round?

What would be problem rating of E1 ? 800 ?

why nlogn solution give TLE on E2?

where to access the editorials of #744 (Div.3)?

Great round. But I would have appreciated some drawings in G, as in C.

RIP my rating . I was trying right shift in problem B :')

I didn't able to solve any question By the way I try solve the first question but unable

As I remember, Problem D was already used in past contests with different statement but same idea

It would have been better if F had integers upto $$$10^9$$$ instead of 0's and 1's .

The problem would have been similar to this and we would have to just process Range AND Queries on individual components

My reaction seeing that the guy name was Casimir:

The problems were literally all over the place.
Even deciding which ones to solve was more difficult than E1.

How to solve G? something like dp?

Can someone elaborate the problem C please, still I can't understand what it wants!!

THE EASIEST E1 EVER! :)

Can someone help me to figure out the mistake with my logic/code for problem E2?(thanks in advance)

Logic: During each insertion, let the current element be K, we add min(number of elements strictly lower than K, number of elements strictly greater than K) to the answer. I implemented this using PBDS multiset.

my submission

T~T,It was another very violent topic, and then I saw that I finished it in three minutes, but I felt good on the whole

How to solve G?

A to F easy solutions with Code and Explanations Happy Coding.

void solve() {
    int a = 0, b = 0, c = 0;
    string s;
    cin >> s;
    for(auto c: s) {
        if(c == 'B') b ++;
    }
    if(2 * b == s.length()) {
        cout << "YES\n";
    }
    else {
        cout << "NO\n";
    }
}

void solve() {
    int n;
    cin >> n;
    vector<int> v(n);
    for(int i = 0; i < n; i ++) {
        cin >> v[i];
    }
    vector<vector<int>> ops;
    for(int i = 0; i < n; i ++) {
        int ind = i;
        int ele = v[i];
        for(int j = i; j < n; j ++) {
            if(v[j] < ele) {
                ele = v[j];
                ind = j;
            }
        }
        int dis = ind - i;
        if(dis > 0) {
            ops.push_back({i + 1, ind + 1, dis});
            vector<int> temp = {v[ind]};
            for(int j = i; j < ind; j ++) {
            temp.push_back(v[j]);
            }
            for(int j = i; j <= ind; j ++) {
            v[j] = temp[j -i];
            }
        }
        
    }
    cout << ops.size() << endl;
    
    for(auto it: ops) {
        for(auto i: it) {
            cout << i << " "; 
        }
        cout << endl;
    }
}

int mat[20][20];
 
bool isthis(vector<string> v, int i, int j, int K, int n, int m) {
    int x = j;
    int y = j;
    int k = 0;
    vector<vector<int>> pos;
    while(i >= 0  && y < m && x >= 0) {
        if(v[i][x] == '.' || v[i][y] == '.') {
            break;
        }
        pos.push_back({i, x});
        pos.push_back({i, y});
        k  ++;
        i --;
        x --; 
        y ++;
    }
    if(k < K) {
        return 0;
    }
    for(auto it: pos) {
        mat[it[0]][it[1]] = 1;
    }
    return 1;
}
void solve() {
    int n, m, k;
    cin >> n >> m >> k;
    vector<string> v(n, string(m, '.'));
    memset(mat, 0, sizeof(mat));
    int ans = 0;
    for(int i = 0; i < n; i ++) {
        cin >> v[i];
        for(int j = 0; j < m; j ++) {
            isthis(v, i, j, k + 1, n, m);
        }
    }
    for(int i = 0; i < n; i ++) {
        for(int j = 0; j < m; j++) {
            if(v[i][j] == '*' && !mat[i][j]) {
                cout << "NO\n";
                return;
            }
        }
    }
    cout << "YES\n";
}

void solve() {
    int n, m, k;
    cin >> n;
    int i = 1;
    priority_queue<vector<int>> pq;
    for(; i <= n ; i ++) {
        cin >> k;
        if(k)
        pq.push({k, i});
    }
    vector<vector<int>> ops;
    while(pq.size() > 1) {
        auto i1 = pq.top(); pq.pop();
        auto i2 = pq.top(); pq.pop();
        ops.push_back({i1[1], i2[1]});
        i1[0] --;
        i2[0] --;
        if(i1[0]) {
            pq.push(i1);
        }
        if(i2[0]) {
            pq.push(i2);
        }
    }
    cout << ops.size() << endl;
    for(auto it: ops) {
        for(auto i: it) {
            cout << i << " ";
        }
        cout << endl;
    }
    
}

void solve() {
    int n;
    cin >> n;
    deque<int> dq;
    int j;
    for(int i = 0; i < n; i ++) {
        cin >> j;
        if(!dq.empty() && j < dq.front()) {
            dq.push_front(j);
        }
        else {
            dq.push_back(j);
        }
    }
    while(!dq.empty()) {
        cout << dq.front() << " ";
        dq.pop_front();
    }
    cout << endl;
}

#define ordered_set tree<pair<int,int>, null_type,less<pair<int,int>>, rb_tree_tag,tree_order_statistics_node_update>
typedef long long int  ll;
ll P = 1e9 + 7;
 
void solve() {
    ll n;
    cin >> n;
    deque<ll> dq;
    ll j;
    ordered_set X;
    map<ll,ll> mp;
    ll ans = 0; 
    for(int i = 0; i < n; i ++) {
        cin >> j;
        int less = X.order_of_key({j, -1});
        int tot = i;
        int great = tot - less - mp[j];
        // cout << great << " " << less << " " << j << endl;
        if(great < less) {
            dq.push_back(j);
            ans += great;
        }
        else {
            dq.push_front(j);
            ans += less;
        }
        X.insert({j, i});
        mp[j] ++;
    }
    
    // while(!dq.empty()) {
    //     cout << dq.front() << " ";
    //     dq.pop_front();
    // }
    // cout << endl;
    cout << ans << endl;
}

void solve() {
    ll n, d;
    cin >> n >> d;
    vector<ll> vis(n), v(n);
    for(ll i = 0; i < n; i ++) {
        cin >> v[i];
    }
    ll ans = 0;
    for(ll i = 0; i < n; i ++) {
        ll curr = i;
        vector<ll> t;
        ll o = 1;
        while(!vis[curr]) {
            t.push_back(v[curr]);
            o &= v[curr];
            vis[curr] = 1;
            curr += d;
            curr %= n;
        }
        ll k = t.size();
        if(k == 0) continue;
        if(o) {
            cout << "-1\n";
            return;
        }
        
        vector<vector<ll>> bits(1, vector<ll>(2*k, INT_MAX));
        
        for(ll i = 0; i < k; i ++) {
            ll val = t[i];
            for(ll j = 0; j < 1; j ++) {
                if((1<< j) & t[i]) {
                    if(i > 0)
                    bits[j][i] = bits[j][i - 1];
                }
                else {
                    bits[j][i] = i;
                }
            }
            t.push_back(t[i]);
        }
        
        for(ll i = k; i < t.size(); i ++) {
            ll val = t[i];
            for(ll j = 0; j < 1; j ++) {
                if(t[i] == 1) {
                    bits[j][i] = bits[j][i - 1];
                }
                else {
                    bits[j][i] = i;
                }
                ans = max(ans, i - bits[j][i]);
            }
            
        }
        
    }
    
    cout << ans << endl;
}
 

Why am I not able to hack any solution or even been able to lock any problem during Codeforces Round #744 (Div. 3) ?

Nice round, with great problems.

Although the order of problems could be better, the problems were great!

Thanks :)

Most unbalanced div $$$3$$$ round ever :(

The difficulty was like $$$A < E1 < B < D < C$$$ as I felt.

In problem F, I have used the fact that once some a[index] becomes 0, it will always remain 0 and will turn a[(index+d)%n] to 0 as well..

So, at each step if there's no new index where 0 is formed.. ans will be -1, else we can store these new indices to use them in the next step till all indices are converted 0.

So, if at each step "X" new indices are formed.. the process will go on for N/X iterations .. making it X*(N/X)

I am not pretty sure about this complexity and method.. Can someone provide a counter case/hack it, or affirm it ?

Submission

Who made these test cases? E1 hacks are going insane with very straightforward hack.

Can someone explain approach for C plase

B submission WA I was trying to solve be for more than 1 hour but it was still giving the wrong answer. The codeforces engine was giving a different answer and my machine was giving different. Mine was correct. I later submitted the problem with very minor change and it got accepted. It was some undefined behaviour I guess, if anybody could explain why that happened, I would be really grateful. Accepted Solution

please take a look into hack #758216, the result is "unexpected verdict".
(I mistakenly submit invalid input, then I got such result. Maybe the validator of G is wrong.)

I have tried a video solution for the problem F: https://www.youtube.com/watch?v=8qC3qyQsE8s Hope it will help you if you need it.

Hi any one could help me to solve problem D, give me the idea or full code, this is my code i got WA, cause their is no tutorial, thanks in advance, and sorry for my English. void solve() {
int t; cin >>t; while(t--) { int n; cin >>n; vii v(n); lp(i, n) { cin >>v[i].f; v[i].s = i+1; } sort(v.rbegin(), v.rend()); vii ans; int i=0, j=1; while(v[i].f&&v[j].f) { ans.pb({v[i].s, v[j].s}); v[i].f--; v[j].f--; for(int a=j;a+1<n && v[a].f < v[a+1].f; a++) swap(v[a], v[a+1]); for(int a=i;a+1<n && v[a].f < v[a+1].f; a++) swap(v[a], v[a+1]);

}
    cout <<sz(ans)<<"\n";
    rep(i, ans) {
        cout <<ans[i].f<<" "<<ans[i].s<<"\n";
    }
}

}

I would like to report a system bug in problem G.

When I submit my solution, it gets time limit exceeded at test set 22. But when I looked at test set 22, it have three test cases, and first one array length is 10000. But problems says the total number of G does not exceed 10000, so it is not a valid test set.

I look at others solutions passed during contest, and the total number is 18. So test set 22 is not generated by authors, but by hackers after the contest.

Then I tried to generate an invalid test set (3 test cases with total number of n 30000) and hacked others code (I only hacked people who are not officially participate the contest), they all succeed.

Therefore, please remove these test sets that sum of the n > 10000, and rejudge these hacked solutions for problem G. It is unfair for participated who solved problem G but exe time is larger than 333ms.

It's rare to see something like this : same same same same same same same same same same same same same same same ....... code.

Thnx for great round, even though I wasn't so luky. Anyway I may have misunderstood problem B, I used Bubble sort considering swaps as d = 1 circular shifts, on paper it all make sence but yet it get me wrong answer on test 2. this is my submission 130155379 , could any good one of you help me with it ?

I'm new here, so the round should be rated for me but, the contest is showing itself in the unrated section in my profile contests, also I'm not in the standings. I did solve 4 questions during the contest. Can anyone tell me what's this issue?