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

Why not thank me for participating?

Excited and hopefully the problem's statement will be short and precise just like the announcement! <3

Grey testing?

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RAMADAN contest starts 15:35UTC+2. Please

Hmmm you didn't thank us lol

do not have a point of 1900 or higher in the rating. So div 2 or div 3 ?

date is wrong

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

Ramadan>contest

By the way thanks for the March 19's div3 its on the right time

why is there such a big gap (20 days) between 2 contests?? Will more contests be added in between?

UPD: Another contest added

Hopefully more contests gets added up in between.

What does trusted participant mean?

First contest during Ramadan!

I hope the tasks will be interesting

And Good Luck for every parcipicant!

Sorry Codeforces, I have to attend night-prayer at that time. so, No contest for me for the next 30 days.

I hope to become specialist after this round.

"adventures of a restless mathematician"

Mathforces Incoming. Brace yourselves

In the last few days, why Div3 contest has been hosted so frequently than before?

exciting to become an Expert!

GL everybody :)))

I hope to solve as many problems as possible :DD

Hope reach pupil after this round

Good luck for everyone !!!!

Why no thanks for gray writers/testers?

Negative delta, HERE WE GO

gl everyone :>

thanks for information;

Excited to give this contest on my birthday!!!

If I become pupil during Ramadan, I will convert to Muslim from Hindu

Hope to solve only A. B TO G will be so hard.

Good luck!

RAMADAN mubark :)

Expert please

Rudolf and Bernard? Game theory on problem E?

I wish this contest i could improve the score ！ because i have lose four times till now

Problem E is one of the worst problems i have ever read

E has an unusual distance definition and it has not been presented in the russian version for more than half an hour

I spent more time in B than problems E and F due to my stupid mistake.

bad B, C, D, E, F, G!!!!

Binary search doesn't work for F ?

My private Screencast.. A,B,C,D,E Video Solutions here: https://www.youtube.com/watch?v=hSNp4xnn9lc

Screencast with commentary (set video quality to HD to be able to read my code)

Problem G is nice.

E seem very hard (at least for me) are there other simple solutions not involving dp with segment tree or sparse table?

Can someone explain the 4th test case in problem D.

Like how is it 2 3 5 and not 1 2 3 5?

RIP all who got WA on test 2 in F :(

I don't know which case I was missing. Can anyone debug my submission : https://codeforces.net/contest/1941/submission/250809941

Got trolled by problem F (2 wrong submissions) because (a[i] + a[i+1]) / 2 overflows int :(

Let this be a lesson to use std::midpoint... (or in Java, a[i] + (a[i+1] - a[i]) / 2)

I could only get TLA on test 3 for F, which trick was needed to reduce complexity ? FFT ?

For problem G I made a simple Dijkstra where the cost is determined by the size of a std::set which contains all the colors of the edges I've been through. Does anyone have an idea why it doesn't pass Test 3?

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

#define el '\n'
#define int int

struct edge {
    int dst{0}, c{0};
};

struct pqel {
    set<int> cost{};
    int node{0};

    bool operator<(const pqel& i) const {
        return this->cost.size() > i.cost.size();
    }
};

inline void solve()
{
    int n, m; cin >> n >> m;
    vector<edge> adj[n + 1];

    for (int i = 1; i <= m; i++) {
        int u, v, c; cin >> u >> v >> c;
        adj[u].push_back({v, c});
        adj[v].push_back({u, c});
    }

    int b, e; cin >> b >> e;

    vector<bool> visited(n + 1);
    priority_queue<pqel> pq;
    pq.push({{}, b});

    while (!pq.empty()) {
        auto t = pq.top(); pq.pop();
        if (t.node == e) {
            cout << t.cost.size() << el;
            break;
        }
        visited[t.node] = 1;

        for (auto child : adj[t.node]) if (!visited[child.dst]) {
            set<int> s = t.cost; s.insert(child.c);
            pq.push({s, child.dst});
        }
    }
}

int32_t main()
{
    int t;
    cin >> t;
    while (t--)
        solve();
}

Excuse me guys, but who can help me find mistake in D?

My answer is different with correct answer in only one number, and I coulnd't find mistake.

Here is my code:

void solve() {
	int n, m, x;
	cin >> n >> m >> x;
	vector<int> ans;
	int r; char c;
	cin >> r >> c;
	if (c == '0') {
		ans.push_back((x + r)%n + 1);
	} else if (c == '1') {
		int frm = (x-r+n)%n;
		ans.push_back(frm + 1);
	} else if (c == '?') {
		ans.push_back((x + r)%n + 1);
		int frm = (x-r+n)%n;
		ans.push_back(frm + 1);
	}
	for (int i = 0; i < m-1; i ++) {
		cin >> r >> c;
		if (c == '0') {
			for (auto el : ans) {
				el = (el + r)%n + 1;
			}
		} else if (c == '1') {
			for (auto el : ans) {
				int frm = (el-r+n)%n + 1;
				el = frm;
			}
		} else if (c == '?') {
			vector<int> v;
			for (auto el : ans) {
				v.push_back((el + r)%n + 1);
				int frm = (el-r+n)%n + 1;
				v.push_back(frm);
			}
			ans = v;
		}
	}
	set<int> res;
	for (auto i : ans) {
		i --;
		if (i == 0) {
			res.insert(n);
		} else {
			res.insert(i);
		}
	}
	cout << len(res) << nl;
	for (auto i : res) {
		cout << i << " ";
	}
}

I will be very grateful to anyone who offers a helping hand

Can anyone give me some insights over the Solution of Problem — F Rudolf and Imbalance

Is there anyone ignore the "consecutive" in problem E like me ._.

G was a nice problem

Can't help but point out that C has more ACs than B tho..

WT compilation error !!

Can't wait to become Expert!

I couldn't implement it in time, but I just wanted to make sure my strategy is correct for E.

Let row_ans[r] represent the minimum cost for some row. We can use prefix sums to calculate some contiguous row_ans and choose the minimum in O(n-k) time. The minimum will be the answer.

As for calculating row_ans[r], we use dp to calculate the minimum cost from dp[r][c] to dp[r][m]. row_ans[r] = dp[r][1].

Simmply apply dfs over dp[r][c] and check the minimum cost between dp[r][c] and dp[r][c+1], dp[r][c+2], ..., dp[r][c+d+1].

Is there anything more/wrong?

someone tell the approach of PROBLEM D

Again missed cyan by 2 points. Rip my life

(haven't given this contest but) wanted to ask which topics do i need to learn to solve div 3/4's F and g?

I tried F instead of E as seemed easier but failed on test2.

here's the submission (code is clean)
any help is appreciated.

"Note that the penalty for the wrong submission in this round is 10 minutes." Does it mean I can't submit for the next 10 min? or is it anything else?

Is there anyway to solve problem E with memoization? Just curious.

Problem A — Simple sort and binary search.

Problem B — Note that 1st element can only be modified by operations on element 2. Accordingly iterate over the array, simulate the operations on each, and check the last 2 elements for 0. In any case, element value goes < 0, answer is not possible.

Problem C — Simple substring search. First, count for mapie (requires only 1 operation). Then check for rest of the possiblities (pie, map).

Problem D — Let dp(i,j) represents whether all the m turns result in player j having the ball, if we are at move i and currently player j has the ball. Do a simple recurive dp, and final answer is the count of dp[i][m] == 1 over all i players.

Problem E — For each row, let dp(i) represent the min. cost to place supports, such that we place a support at a[row][j]. dp(i) can be calculated as min j from i-d-1 to i-1. Use segment tree to speed up this calculation. For every row, cost for that is dp(m). Final answer is a subarray of size k with minimum sum, that can be done using simple prefix sums.

Guys fft tag for B wtf?

Admit it, who solved B using fft?

Does hacking points contribute in rating?

**Dear Codeforces Community ** Please can anyone tell me why this code give wa on test 2 https://codeforces.net/contest/1941/submission/250799602

and when i just update the vector size with n+1 and m+1 then it gives me tle on test 6

https://codeforces.net/contest/1941/submission/250822673

the difference between both the codes is just that instead of using vector of size [n][m] i took [n+1][m+1]??

Someone Please answer this python related question regarding problem D. For the input details about m throws, if I take the input as s = input().split(), dist,dir = int(s[0]),s[1] it gets accepted. But during the contest I took it as s = input().rstrip() ,dist,dir = int(s[0]),s[2] (I thought s[1] is the white space?), it gives WA on test 3. Everything else in both the codes is the same. Why is this the case? Can't believe I did not solve a problem because of this :(

I tried D using recursion (gave tle ) then applied dp, here is my code 250762239. Can someone pls tell why it gave wa ?

Similar problems : G and arc061_c