Tune in at twitch.tv/the__tourist at around 22:30 MSK, 11 Jan 2022 to watch me solving SnarkNews Winter Series 2022 Round 1 live! First I will do the round competitively without much interaction, and I'll be up for discussing the problems on stream afterwards.

SnarkNews Winter/Summer Series (SNWS/SNSS) is organized by snarknews and consists of 5 rounds. Each round is a virtual 6-problem 80-minute contest open for 10 days. The series is open to all, but problem statements are in Russian only. On stream, I'll read the problem statements automatically translated to English.

To make the stream more fun and for easier understanding of what will be going on, you're welcome to do the round yourself beforehand! If you don't understand Russian, you can also compete using automatic translators. Alternatively, you may just read the problems without solving them. In any case, don't discuss the problems in Codeforces comments before the round window ends.

Tentative schedule of future streams:

• Round 2 (contest link): 22:30 MSK, 16 Jan 2022
• Round 3 (contest link): 22:30 MSK, 21 Jan 2022
• Round 4 (contest link): 22:30 MSK, 26 Jan 2022
• Round 5 (contest link): 22:30 MSK, 31 Jan 2022

I might be streaming at other times too, so be sure to follow me on Twitch to get instant notifications.

See you on stream!

Topcoder Open 2021 Algorithm Semifinal 2 is right around the corner, starting in less than 5 minutes!

The competitors are Benq aka bqi343, Petr, scott_wu, neal aka neal_wu, SpyCheese, maroonrk aka maroon_kuri, krijgertje, and Heltion.

The top 4 advance to the Finals. The advancers from Semi 1 are ecnerwala, tourist, Um_nik, and ACRush.

Watch the live broadcast on YouTube and Twitch, featuring Pena, Egor, tourist, and ksun48!

Topcoder Open 2021 Algorithm Semifinal 1 is right around the corner, starting in less than 5 minutes!

The competitors are tourist, ecnerwala aka ecnerwal, ACRush, hos.lyric aka lyrically, Um_nik, ko_osaga aka gs14004, PavelKunyavskiy aka kuniavski, and never_giveup aka grumpy_gordon.

Watch the live broadcast on YouTube and Twitch, featuring scott_wu, Petr, and krijgertje!

Hope you enjoyed the round!

Hello again!

VK Cup 2021 - Final (Engine) starts very soon: on Aug/22/2021 15:05 (Moscow time). Today, 32 best contestants of the elimination round will be fighting for cash prizes and eternal glory.

You can follow the course of the contest and root for your favorite contestants via this link.

Everyone except for VK Cup 2021 finalists is invited to Codeforces Round #740 (Div. 1, based on VK Cup 2021 - Final (Engine)) and Codeforces Round #740 (Div. 2, based on VK Cup 2021 - Final (Engine)) that start a couple of days later: on Aug/24/2021 17:35 (Moscow time). The rounds will be rated for everyone.

All the problems were authored and prepared by me. Big thanks to everyone without whom this round would not be possible: KAN, PavelKunyavskiy, scott_wu, xiaowuc1, Monogon, Aleks5d, lperovskaya, MikeMirzayanov. Special thanks to s-quark (2nd place of the first ever VK Cup 2012!) for inspiring problem titles.

You will be given 6 problems and 2 hours 30 minutes to solve them in both divisions. It is recommended to read all the problems. Good luck!

UPD: Scoring distribution in the VK Cup finals: 500 — 1250 — 1500 — 2000 — 3000 — 3500

UPD2: Congratulations to the winners of the VK Cup 2021 Final Round!

1. never_giveup
2. Maksim1744
3. Um_nik
4. SpyCheese
5. Nebuchadnezzar
6. vepifanov
7. Golovanov399

UPD3: Division 1 round will be held on the VK Cup 2021 Finals problem set without any changes.

Scoring distribution for Div. 1: 500 — 1250 — 1500 — 2000 — 3000 — 3500

In Division 2 problems BDEF will match problems ABCD of Div. 1. Problems A and C of Div. 2 will be similar to problems F and E of Div. 1 (albeit being much easier). Besides that, problem D of Div. 2 will have a subtask with lower constraints than the original problem.

Scoring distribution for Div. 2: 500 — 1250 — 1250 — (1500 + 1000) — 2500 — 3500

As a reminder, the standings of the VK Cup Finals are available via this link — feel free to try gaining an advantage using all the information available before the round :)

UPD4: Editorial is available.

Hope you enjoyed the round! Editorials for all problems are out now. Also check out ecnerwala's stream where we went through individual problems and discussed the contest as a whole: https://www.youtube.com/watch?v=5Q4tGWT7p7I.

Hello, Codeforces!

Welcome to the Codeforces Round #733 (Div. 1 + Div. 2, based on VK Cup 2021 - Elimination (Engine)) that will start on Jul/17/2021 17:35 (Moscow time). It will be a combined rated round for both divisions.

This round is a mirror of VK Cup 2021 Elimination. VK Cup is an annual championship for Russian-speaking competitors organized by VK — a social networking service based in Saint Petersburg and the most popular website in Russia. VK Cup started in 2012 and has grown to be a four-track competition in competitive programming, ML, design, and mobile development.

All the problems were authored and prepared by me. Big thanks to everyone without whom this round would not be possible: PavelKunyavskiy, KAN, lperovskaya, ksun48, Sert, Aleks5d, MikeMirzayanov.

You will be given 8 problems and 3 hours to solve them. It is recommended to read all the problems. Good luck!

UPD: Scoring distribution: 500 — 750 — 1000 — 1500 — 2000 — 2750 — 3750 — 4750

UPD2: Congratulations to the winners!

VK Cup 2021 — Elimination (Engine):

1. Um_nik
2. Petr
3. Endagorion
4. Golovanov399
5. mhq

Codeforces Round #733:

1. jiangly
2. ecnerwala
3. Radewoosh
4. maroonrk
5. Benq

Editorial of problems A-E is out, problems F-H will appear later.

UPD3: Editorial now contains problems F-H as well.

Tune in to my Twitch to watch me solve today's Codeforces Round 672 (Div. 2) virtually.

UPD: Video on YouTube.

Hey there!

During my last stream (link to YouTube), besides the expected SNSS Round 5, I did Codeforces Round 669 (Div. 2) virtually trying to explain most of my thoughts in the process. I'd say it went pretty well!

Tomorrow I'll hold another stream solving the most recent Codeforces Div. 2 rounds: Round 670 and Educational 95. I might also do today's AtCoder Beginner Contest 178.

I'm planning to go live right after Educational 95 finishes — that is, around 19:45 MSK.

A question is, given that I will do both Round 670 and Educational 95, which one should I do first? Vote here :)

As usual, the stream will be live on my Twitch, make sure to follow and get instant notifications. Stream recording will be posted to my YouTube afterwards.

See you!

It's this time of the year again!

Tune in at twitch.tv/the__tourist at around 21:45 MSK, 21 Aug 2020 to watch me solving SnarkNews Summer Series 2020 Round 1 live! First I will do the round competitively without much interaction, and I'll be up for discussing the problems on stream afterwards.

SnarkNews Winter/Summer Series (SNWS/SNSS) is organized by snarknews yearly and consists of 5 rounds. Each round is a virtual 6-problem 80-minute contest open for 10 days. The series is open to all, but problem statements are in Russian only. Unlike last series, I'll be reading problem statements automatically translated to English on stream.

To make the stream more fun and for easier understanding of what will be going on, you're welcome to do the round yourself beforehand! If you don't understand Russian, you can also compete using automatic translators. Alternatively, you may just read the problems without solving them. In any case, don't discuss the problems in Codeforces comments before the round window ends.

Tentative schedule of future streams:

• Round 2 (contest link): 21:45 MSK, 25 Aug 2020
• Round 3 (contest link): 21:45 MSK, 5 Sep 2020
• Round 4 (contest link): 21:45 MSK, 7 Sep 2020
• Round 5 (contest link): 21:45 MSK, 9 Sep 2020

I might be streaming at other times too, so be sure to follow me on Twitch and get instant notifications.

See you on stream!

UPD: Round 1 stream is available on my channel: link. Round 2 stream is starting as planned, in 8 hours — be sure to join! Here is the contest link if you'd like to do the contest or read the problems beforehand.

UPD2: Round 2 stream: link. Unfortunately, Round 3 has not started yet — therefore, the next streams have to be postponed. Follow this blog and my Twitch for updates.

UPD3: New dates of Rounds 3-5 (and hence my streams) have been announced!

UPD4: Just a friendly reminder: Round 3 ends in less than 24 hours, and thus my next stream is coming tomorrow! Also note that Rounds 4 and 5 are about to end as well, there are just two days between consecutive rounds.

UPD5: Round 3 stream: link. Round 4 stream is coming in less than 4 hours from now!

UPD6: Round 4 stream: link. The last stream of the series, Round 5, is coming today in less than 3 hours!

UPD7: Round 5 stream: link (with virtual Codeforces Round 669 (Div. 2) as a practice before SNSS). This was the last stream of the series, thank you for tuning in! However, this was not the last stream of the season — check this blog post for more.

XX Open Cup Grand Prix of Gomel takes place on Sunday, February 16, 2020, at 11:00 AM Petrozavodsk time.

The links to the contest:

• Division 1
• Division 2

You need an Open Cup login to participate.

I'm the writer of all the problems. Let's discuss them here after the contest!

UPD: Thanks for your participation! Editorial is available.

(Previous episodes: Episode 001, Episode 002, Episode 003, Episode 004)

Hey there, it's time for the final stream of the series!

Tune in at twitch.tv/the__tourist at around 22:45 MSK, 06 Feb 2020 to watch me solving SnarkNews Winter Series 2020 Round 5 live! I'm going to do the round competitively without any interaction, and I'll try to explain the problems in English on stream afterwards.

As usual, I invite you to do the round yourself before I do! If you don't understand Russian, you may compete using automatic translators, or you may just read the problems beforehand without solving them. In any case, don't discuss the problems in Codeforces comments before the stream ends.

See you on stream!

UPD: Video at YouTube. This series is over now! Thanks for watching, and I hope you enjoyed the streams.

(Previous episodes: Episode 001, Episode 002, Episode 003)

Hey there!

Tune in at twitch.tv/the__tourist at around 21:45 MSK, 28 Jan 2020 to watch me solving SnarkNews Winter Series 2020 Round 4 live! I'm going to do the round competitively without any interaction, and I'll try to explain the problems in English on stream afterwards.

As usual, I invite you to do the round yourself before I do! If you don't understand Russian, you may compete using automatic translators, or you may just read the problems beforehand without solving them. In any case, don't discuss the problems in Codeforces comments before the stream ends.

See you on stream!

UPD: Video is available at YouTube.

(Previous episodes: Episode 001, Episode 002)

Hey there!

Tune in at twitch.tv/the__tourist at around 21:45 MSK, 22 Jan 2020 to watch me solving SnarkNews Winter Series 2020 Round 3 live! I'm going to do the round competitively without any interaction, and I'll try to explain the problems in English on stream afterwards.

As usual, I invite you to do the round yourself before I do! If you don't understand Russian, you may compete using automatic translators, or you may just read the problems beforehand without solving them. In any case, don't discuss the problems in Codeforces comments before the stream ends.

See you on stream!

UPD: Thanks for watching! Video is available at YouTube. My performance was remarkably bad, but hopefully that didn't make the stream less fun :)

Episode 001

Hey there!

Tune in at twitch.tv/the__tourist at around 21:45 MSK, 17 Jan 2020 to watch me solving SnarkNews Winter Series 2020 Round 2 live! I'm going to do the round competitively without any interaction, and I'll try to explain the problems in English on stream afterwards.

Just like the last time, I invite you to do the round yourself before I do! If you don't understand Russian, you may compete using automatic translators, or you may just read the problems beforehand without solving them. In any case, don't discuss the problems in Codeforces comments before the stream ends.

See you on stream!

UPD: Video at YouTube. This time with more implementation-oriented problems and worse performance of mine, but clearer sound and more thorough explanations :) Do let me know what you think.

The next stream is planned at the end of SNWS 2020 Round 3: 21:45 MSK, 22 Jan 2020.

Hey there!

Tune in at twitch.tv/the__tourist at around 21:45 MSK, 12 Jan 2020 to watch me solving SnarkNews Winter Series 2020 Round 1 live! First I will do the round competitively without any interaction, and I'll be up for discussing the problems on stream afterwards.

SnarkNews Winter/Summer Series (SNWS/SNSS) is organized by snarknews yearly and consists of 5 rounds. Each round is a virtual 6-problem 80-minute contest open for 10 days. The series is open to all, but problem statements are in Russian only. Nevertheless, I'm going to discuss the problems in English.

To make the stream more fun and for easier understanding of what will be going on, you're welcome to do the round yourself before I do! If you don't understand Russian, you may compete using automatic translators. Alternatively, you may just read the problems beforehand without solving them. In any case, don't discuss the problems in Codeforces comments before the stream ends.

See you on stream!

UPD: The stream is over. If everything goes well, the next stream will happen at the end of SNWS 2020 R2: 21:45 MSK, 17 Jan 2020. Do let me know whether you liked it and any other thoughts/suggestions in comments!

UPD2: The video of the stream is now available at YouTube.

We will hold AtCoder Grand Contest 041. This is the last contest of 2019 that counts for AtCoder Race Ranking.

• Contest URL: https://atcoder.jp/contests/agc041
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20191228T2100&p1=248
• Duration: 150 minutes
• Number of Tasks: 6
• Writer: tourist
• Rated range: All

The point values will be 300 — 700 — 900 — 1200 — 1600 (800 + 800) — 2000.

We are looking forward to your participation!

Enjoy!

#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  int flag = 1;
  for (int i = 0; i < n; i++) {
    int x;
    cin >> x;
    if (x % 2 == 0) {
      cout << x / 2 << '\n';
    } else {
      cout << (x + flag) / 2 << '\n';
      flag *= -1;
    }
  }
  return 0;
}

#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<int> a(n), b(n);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    --a[i];
  }
  for (int i = 0; i < n; i++) {
    cin >> b[i];
    --b[i];
  }
  vector<int> pos(n);
  for (int i = 0; i < n; i++) {
    pos[b[i]] = i;
  }
  vector<int> c(n);
  for (int i = 0; i < n; i++) {
    c[i] = pos[a[i]];
  }
  int mx = -1, ans = 0;
  for (int i = 0; i < n; i++) {
    if (c[i] > mx) {
      mx = c[i];
    } else {
      ++ans;
    }
  }
  cout << ans << '\n';
  return 0;
}

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<pair<int, int>, pair<int, int> > ii;

int main(){
    int n;
    cin >> n;
    
    vector<ii> v(n);
    for (int i = 0; i < n; i++){
        cin >> v[i].first.first >> v[i].first.second >> v[i].second.first;
        v[i].second.second = i + 1;
    }
    
    while(!v.empty()){
        sort(v.begin(), v.end());
        int x = v.back().first.first;
        int y = v.back().first.second;
        int z = v.back().second.first;
        int pos = v.back().second.second;
        v.pop_back();
        int ind = 0;
        ll d = 1e10;
        for (int i = 0; i < (int) v.size(); i++){
            ll dist = abs(v[i].first.first - x);
            dist += abs(v[i].first.second - y);
            dist += abs(v[i].second.first - z);
            if (dist < d){
                d = dist;
                ind = i;
            }
        }
        cout << pos << " " << v[ind].second.second << endl;
        v.erase(v.begin() + ind);
    }
}

#include <bits/stdc++.h>

using namespace std;

const int D = 3;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<vector<int>> p(n, vector<int>(D));
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < D; j++) {
      cin >> p[i][j];
    }
  }
  auto Solve = [&](auto& Self, vector<int> ids, int k) {
    if (k == D) {
      return ids[0];
    }
    map<int, vector<int>> mp;
    for (int x : ids) {
      mp[p[x][k]].push_back(x);
    }
    vector<int> a;
    for (auto& q : mp) {
      int cur = Self(Self, q.second, k + 1);
      if (cur != -1) {
        a.push_back(cur);
      }
    }
    for (int i = 0; i + 1 < (int) a.size(); i += 2) {
      cout << a[i] + 1 << " " << a[i + 1] + 1 << '\n';
    }
    return (a.size() % 2 == 1 ? a.back() : -1);
  };
  vector<int> t(n);
  iota(t.begin(), t.end(), 0);
  Solve(Solve, t, 0);
  return 0;
}

#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<int> a(3 * n);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    a[i + n] = a[i + 2 * n] = a[i];
  }
  vector<int> ans(3 * n);
  vector<int> st_max;
  vector<int> st_min;
  for (int i = 3 * n - 1; i >= 0; i--) {
    while (!st_max.empty() && a[st_max.back()] < a[i]) {
      st_max.pop_back();
    }
    while (!st_min.empty() && a[st_min.back()] > a[i]) {
      st_min.pop_back();
    }
    int low = 0, high = (int) st_min.size();
    while (low < high) {
      int mid = (low + high) >> 1;
      if (a[st_min[mid]] * 2 < a[i]) {
        low = mid + 1;
      } else {
        high = mid;
      }
    }
    int nxt = 3 * n;
    if (low > 0) {
      nxt = min(nxt, st_min[low - 1]);
    }
    if (!st_max.empty()) {
      nxt = min(nxt, st_max.back());
    }
    if (nxt < 3 * n && a[nxt] >= a[i]) {
      ans[i] = ans[nxt];
    } else {
      ans[i] = nxt;
    }
    st_min.push_back(i);
    st_max.push_back(i);
  }
  for (int i = 0; i < n; i++) {
    if (i > 0) {
      cout << " ";
    }
    cout << (ans[i] == 3 * n ? -1 : ans[i] - i);
  }
  cout << '\n';
  return 0;
}

#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  int x = 1;
  while (x <= n) {
    if (n == x || n == x + 1) {
      cout << 1 << '\n';
      return 0;
    }
    if (x % 2 == 0) {
      x = x + 1 + x;
    } else {
      x = (x + 1) + 1 + x;
    }
  }
  cout << 0 << '\n';
  return 0;
}

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

const int MOD = 998244353;
const int MAX = 3610;
ll dp1[MAX][MAX], dp2[MAX][MAX];
int has1[MAX], has2[MAX];
ll fac[MAX], c[MAX][MAX];
int n, m, k;

void make(int n){
    dp1[0][0] = 1;
    for (int i = 1; i <= n; i++){
        for (int j = 0; j <= m; j++){
            dp1[i][j] = dp1[i - 1][j];
            if (j && i >= 2 && has1[i] == 0 && has1[i - 1] == 0){
                dp1[i][j] += dp1[i - 2][j - 1];
            }
            dp1[i][j] %= MOD;
        }
    }
}

int main(){
    cin >> n >> m >> k;
    int t = max(n, m) + 1;
    vector<ll> f(t);
    for (int i = 1; i <= k; i++){
        int a, b, c, d;
        cin >> a >> b >> c >> d;
        if (has1[a] || has1[c] || has2[b] || has2[d]){
            cout << 0 << endl;
            return 0;
        }
        has1[a] = has1[c] = has2[b] = has2[d] = 1;
    }
    int N = n, M = m;
    for (int i = 1; i <= n; i++){
        N -= has1[i];
    }
    for (int i = 1; i <= m; i++){
        M -= has2[i];
    }
    make(n);
    swap(dp1, dp2);
    swap(has1, has2);
    make(m);
    swap(dp1, dp2);
    swap(has1, has2);
    c[0][0] = 1;
    f[0] = 1;
    for (int i = 1; i < t; i++){
        f[i] = (f[i - 1] * i) % MOD;
        c[i][0] = c[i][i] = 1;
        for (int j = 1; j < i; j++){
            c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
            if (c[i][j] >= MOD){
                c[i][j] -= MOD;
            }
        }
    }
    ll ans = 0;
    for (int i = 0; (i << 1) <= N; i++){
        for (int j = 0; (j << 1) <= M; j++){
            int have1 = N - 2 * i;
            int have2 = M - 2 * j;
            ll res = dp1[n][i] * dp2[m][j];
            res %= MOD;
            res *= c[have1][j];
            res %= MOD;
            res *= c[have2][i];
            res %= MOD;
            res *= f[i];
            res %= MOD;
            res *= f[j];
            res %= MOD;
            ans += res;
        }
    }
    ans %= MOD;
    cout << ans << endl;
}

#include <bits/stdc++.h>

using namespace std;

#ifdef LOCAL
    #define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
    #define eprintf(...) 42
#endif

using ll = long long;
using ld = long double;
using D = double;
using uint = unsigned int;
template<typename T>
using pair2 = pair<T, T>;
using pii = pair<int, int>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;

#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second

const int maxn = 200005;
const int maxk = 19;
const int inf = 1e9;

ll a[2 * maxn];
ll psum[2 * maxn];
pair2<int> go[maxk][2 * maxn];
map<ll, int> lst[maxn];
int id[2 * maxn];
int n, k;
ll need;
vector<pair<int, vector<ll>>> answer;

void perform(int l)
{
    int fn = min(l + k, n);
    assert(psum[fn] >= 0);
    ll wassum = psum[fn];
    vector<ll> exchange = vector<ll>(k, need);
    int start = min(n - k, l);
    for (int i = start; i < l; i++) exchange[i - start] = need + a[i];
    exchange[l - start] += -psum[l];
    exchange.back() += psum[fn];
    answer.pb({start, exchange});
    for (int i = l; i < fn; i++) a[i] = 0;
    a[l] += -psum[l];
    a[fn - 1] += psum[fn];
    for (int i = start; i < start + k; i++) psum[i + 1] = psum[i] + a[i];
    assert(wassum == psum[fn]);
}

void restore(int l)
{
    if (l >= n) return;
    if (a[l] == 0 && psum[l] == 0)
    {
        restore(l + 1);
        return;
    }
    int fn = min(l + k, n);
    if (psum[fn] >= 0)
    {
        perform(l);
        restore(l + k - (psum[fn] > 0));
        return;
    } else
    {
        restore(l + k - 1);
        assert(psum[fn] == 0);
        perform(l);
    }
}

int main()
{
    scanf("%d%d", &n, &k);
    for (int i = 0; i < n; i++) scanf("%lld", &a[i]);
    need = accumulate(a, a + n, 0LL);
    assert(need % n == 0);
    need /= n;
    for (int i = 0; i < n; i++) a[i] -= need;
    for (int i = 0; i < n; i++) a[i + n] = a[i];
    partial_sum(a, a + 2 * n, psum + 1);
    pair2<int> ans = {inf, -1};
    for (int j = 0; j < maxk; j++) go[j][2 * n] = {2 * n, 0};
    for (int i = 2 * n - 1; i >= 0; i--)
    {
        int curid = id[i + 1];
        if (lst[curid].count(psum[i]))
        {
            int to = lst[curid][psum[i]];
            go[0][i] = {to, (to - i - 1) / (k - 1)};
        } else
        {
            int to = 2 * n;
            go[0][i] = {to, (to - i + k - 2) / (k - 1)};
        }
        for (int j = 1; j < maxk; j++) go[j][i] = {go[j - 1][go[j - 1][i].fi].fi, go[j - 1][i].se + go[j - 1][go[j - 1][i].fi].se};
        
        if (i < n)
        {
            int to = n + i;
            int cur = i;
            int curans = 0;
            for (int j = maxk - 1; j >= 0; j--) if (go[j][cur].fi <= to)
            {
                curans += go[j][cur].se;
                cur = go[j][cur].fi;
            }
            if (cur < to) curans += (to - cur - 1 + k - 2) / (k - 1);
            ans = min(ans, {curans, i});
        }
        
        id[i] = (2 * n - i) % (k - 1);
        lst[id[i]][psum[i]] = i;
    }
    
    rotate(a, a + ans.se, a + n);
    partial_sum(a, a + n, psum + 1);
    restore(0);
    
    assert((int)answer.size() == ans.fi);
    printf("%d\n", (int)answer.size());
    for (auto &t : answer)
    {
        printf("%d", (t.fi + ans.se) % n);
        for (auto tt : t.se) printf(" %lld", tt);
        printf("\n");
    }
    return 0;
}

#include <bits/stdc++.h>

using namespace std;

#ifdef LOCAL
    #define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
    #define eprintf(...) 42
#endif

using ll = long long;
using ld = long double;
using D = double;
using uint = unsigned int;
template<typename T>
using pair2 = pair<T, T>;
using pii = pair<int, int>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;

#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second

const int maxn = 4005;

vector<int> ss, tt;
char s[maxn], t[maxn];
int n;
vector<int> answer;
int cnt[5];

vector<int> prepare(char *s)
{
    vector<int> ans;
    for (int i = 0; i < 2 * n; i += 2) ans.pb((s[i] - '0') * 2 + (s[i + 1] - '0'));
    return ans;
}

inline void addanswer(int x)
{
    if (x <= 0) return;
    answer.pb(x);
}

void doreverse(vector<int> &v, int l)
{
    reverse(v.begin(), v.begin() + l);
    for (int j = 0; j < l; j++) if (v[j] >= 1 && v[j] <= 2)
    {
        v[j] = 3 - v[j];
    }
}

int main()
{
    int NT;
    scanf("%d", &NT);
    for (int T = 0; T < NT; T++)
    {
        scanf("%s%s", s, t);
        n = strlen(s) / 2;
        ss = prepare(s);
        tt = prepare(t);
        for (auto &t : tt) if (t == 1 || t == 2) t = 3 - t;
        cnt[0] = cnt[1] = cnt[2] = cnt[3] = 0;
        for (auto t : ss) cnt[t]++;
        for (auto t : tt) cnt[t]--;
        if (cnt[0] != 0 || cnt[3] != 0)
        {
            printf("-1\n");
            continue;
        }
        bool found = cnt[1] == 0;
        int before = -1;
        int after = -1;
        for (int i = 1; i <= n && !found; i++)
        {
            cnt[ss[i - 1]]--;
            cnt[3 - ss[i - 1]]++;
            if (cnt[1] == 0)
            {
                before = 2 * i;
                doreverse(ss, i);
                found = true;
            }
        }
        if (!found)
        {
            for (int i = 1; i <= n; i++)
            {
                cnt[ss[i - 1]]++;
                cnt[3 - ss[i - 1]]--;
            }
        }
        for (int i = 1; i <= n && !found; i++)
        {
            cnt[tt[i - 1]]++;
            cnt[3 - tt[i - 1]]--;
            if (cnt[1] == 0)
            {
                after = 2 * i;
                doreverse(tt, i);
                found = true;
            }
        }
        assert(found);
        
        answer.clear();
        addanswer(before);
        for (int i = n - 1; i >= 0; i--)
        {
            int wh = -1;
            for (int j = n - 1 - i; j < n; j++) if (ss[j] == tt[i]) wh = j;
            addanswer(2 * wh);
            doreverse(ss, wh);
            addanswer(2 * wh + 2);
            doreverse(ss, wh + 1);
        }
        addanswer(after);
        
        for (auto t : answer) reverse(s, s + t);
        assert(strcmp(s, t) == 0);
        
        printf("%d ", (int)answer.size());
        for (auto t : answer) printf("%d ", t);
        printf("\n");
    }
    return 0;
}

Hey!

On Oct/16/2019 17:35 (Moscow time) we will host Codeforces Global Round 5.

It is the fifth round of a new series of Codeforces Global Rounds supported by XTX Markets. The rounds are open for everybody, the rating will be updated for everybody.

The round will last for 2 hours 30 minutes, 8 problems are waiting for you, and one of them will be proposed in two versions.

Scoring distribution: 500 — 750 — (750 + 750) — 2000 — 2500 — 3000 — 3750 — 4000

The prizes for this round:

• 30 best participants get a t-shirt.
• 20 t-shirts are randomly distributed among those with ranks between 31 and 500, inclusive.

The prizes for the 6-round series in 2019:

• In each round top-100 participants get points according to the table.
• The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
• The best 20 participants over the whole series get sweatshirts and place certificates.

The problems of this round were developed by me, and here is the list of people who can't take part in the round as they know the problems beforehand:

KAN, Endagorion, arsijo, Rox, lperovskaya, Aleks5d, Learner99, MikeMirzayanov.

Coincidentally, this is also the list of people I'm thankful to for making this round what it is.

The round will be perfectly balanced. As all things should be.

Welcome!

UPD: The round is over! Editorial is here. Congratulations to the winners:

1. Radewoosh
2. Petr
3. 300iq
4. ecnerwala
5. RomaWhite

XIX Open Cup Grand Prix of Gomel takes place on Sunday, February 10, 2019, at 11:00 AM Petrozavodsk time.

The links to the contest:

• Division 1
• Division 2

You need an Open Cup login to participate.

The Division 1 contest also serves as the open qualifying contest for MosCode Festival 2019.

I'm the writer of all the problems. Let's discuss them here after the contest!

The rules for advancement to the onsite finals of TCO 2019 Algorithm have changed from those for TCO 2018:

http://tco19.topcoder.com/home/algorithm/algorithm-rules

This page claims there are "three (3) ways to advance to the Onsite Finals"!

The first way to advance is to take part in SRMs. There are four three-month Online Stages, during which every positive score in an SRM counts towards a global ranking. The best competitor in each Online Stage advances to the onsite finals directly, with the next 10 competitors advancing to Online Round 4 (which is the final qualification round).

The other two ways stay the same. The best 10 competitors (used to be 14 though) advance from Online Round 4, and the best 2 competitors advance from Online Wild Card Round.

The changes seem to be big enough -- and already relevant, since SRM 736 on August 15 (in two days from now) already counts towards Online Stage 1. However, apart from TCO 2019 website I've only seen this information in Topcoder weekly newsletters, and I believe many people have missed it.

What do you think?

XVIII Open Cup Grand Prix of Gomel takes place on Sunday, February 18, 2018, at 11:00 AM Petrozavodsk time.

The link to the contest. You need an Open Cup login to participate.

I'm the writer of all the problems. Let's discuss them here after the contest!

Hello!

Topcoder SRM 728 will be held tomorrow (January 25, 2018).

See what time it starts in your area.

I'm the writer. Everyone is welcome to participate!