This year there will be two separate online qualifier rounds for the two regionals.

The contest for Mathura is from 2pm to 4pm IST on 18th March 2023. Link

The contest for Amritapuri site is from 8pm to 10pm IST on 18th March 2023. Link

Let's use this blog to discuss the rounds after they end.

Hope to see you all on the leaderboard.

Best of Luck everyone!

Kanpur Mathura prelims has to be the worst ICPC contest, probably ever. Imagine setting 4 problems for a team of 3, and so easy that all of them could easily be solved in $$$\lt$$$ 20 minutes total. And then to add icing on the cake the penalty for a single wrong submission is 20 minutes as well

Agree.... feeling sad after making wrong submissions blindly :(

And that surprise "Case 1:" twist was the ultimate test :)

This is just sad. Wait, no, not just sad. Sad and enraging. Great job!

Was this ICPC qualifier or leetcode contest? 0_0

No, leetcode contests are harder.

Enough with the direspect bro, this can’t be accepted,

leetcode contests are much better than this

speedforces

full shit sherlock

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Feeling sorry for your 1 2 2 50.

Can anybody tell why this got TLE?

They added extra tests and rejudged your submission. After rejuding, execution time has not been updated.

just write it iteratively, and/or use booleans rather than max

If you take 10 lakh rupees as cumulative fees for just the prelims, it is just downright shameful coming up with such a problemset. Probably should reassess whether your priority is advancement of CP or just a pitiful money grab

mathura laxmi chit fund

Refund.

Can someone please tell me why this got TLE ?

You can't rely on 2d-vectors where your complexity is $$$\mathcal{O}(N^2 \cdot T)$$$ which is probably $$$8 \cdot 10^8$$$ iterations, with time limit of 3s.

Use 2d-arrays instead.

Thanks a lot!

I'm about to cry

Already did :) Four TLE's because of this lol.

Guess whatidk why, my solution got accepted , i have used 2-D vectors too.

Any idea how many slots are there in kanpur-mathura? I hope there should be 120 seats :/

Lucky you :')

As always, no official info. from them. But if we see last year, Kanpur had 70 seats, so Kanpur + Mathura should be around 120 to 140. Just a guess though.

How to make a 1600 rated problem 1800.

Give input in floating points.

More like 1200 into 1400 but yeah, that was so annoying (:

Speedforces af.

worst contest I have seen

Preparing for ICPC prelims:Can anyone give a testcase that fails this code for B? Cannot understand what is wrong with this approach.

What when s[i] is equal to value at both pointers!

I used the same approch but sill not able to understand why equal value would effect

Try this test case

1

5

abdcd

dcabd

What happened to that tradition of ICPC where one problem is solved by all teams and one problem is not solved by any team Why having prelims as div 69420 contest

How many teams will be selected from each institute ?

Kanpur regionals qualification rules have been updated here

do you have the same for Amritapuri regionals?

Does anyone know how many slots are there for Mathura Regionals?

The quantity of questions was less. More sort of data structure problems.

Friendly remainder: s=s+b not equal to s+=b

Why is nlogn solution giving TLE for XOR sort?

For me it didn't

This gave TLE

Spoiler`#define endl "\n"`

195 ms

I’m jumping off the terrace

after 1st tle even optimized it to o(n), still didn't make it. Our team is jumping off too.

codeWanna hear some fuel-to-fire stuff? Python soln didn't get TLE

CodeHow to solve central subset?

link

Centroid decomposition ig

Let sz(x) mean the size of the subtree rooted at x. Formally $$$sz(x) = 1 + \sum sz(v)$$$ for all children $$$v$$$ of $$$x$$$.

Choose an arbitrary root and walk through the tree normally with a dfs calculating values of $$$sz$$$. For any node where $$$sz(x) \geq \sqrt{n}$$$, add $$$x$$$ to the subset and consider $$$sz(x) = 0$$$ for further calculations.

Why does this work?

For any child $$$v$$$ of $$$x$$$, $$$sz(v) \lt \sqrt{n}$$$, so the distance between any node in this subtree from $$$v$$$ must also be $$$\lt \sqrt{n}$$$. Since $$$v$$$ is a child of $$$x$$$, the distance of any node in the subtree from $$$x$$$ is $$$\lt \sqrt{n} + 1$$$ or in other words $$$\leq \sqrt{n}$$$.

Since $$$sz(x) \geq \sqrt{n}$$$ whenever we perform this, we add at most $$$\frac{n}{\sqrt{n}} = \sqrt{n}$$$ nodes to the subset.

wait so all we have to do is traverse graph and pick every node after root(N) dfs calls? as in this, would work?

Spoileralso could you pls explain the 2nd point under why it would work? why would we end up ading only add root(N) nodes if we pick nodes at every root(N) distance?

1) Pick any spanning tree and root at node $$$1$$$.

2) Pick the node having the max depth, go up $$$\sqrt{n}$$$ for that node following parents, push this one in the answer, and remove that subtree.

3) Do step 2 until the tree is not empty.

Kudos to Amritapuri online round setters, it felt like a fairly nice and balanced round (except for maybe a bit of an aggressive difficulty jump after the first problem). I really liked how cute the solution to problem A is.

Not at all biased by rank 11 in Amritapuri qualifier vs rank 227 in Mathura qualifier :PYeah Amritapuri was relatively better, getting a lower rank didn't hurt in Amritapuri but it did in Mathura ;(

What are the qualification rules for amritapuri?

Did anyone manage to get non-TLE with $$$n \sqrt{n}$$$ on A?

Ya I guess my worst case would be n^(3/2), you can refer here

Will there be additional system testing on the Amritapuri prelims?

is that common?

Nope, full tests are run during contest time.

How many seats are there for kanpur-mathura regionals?

maybe around 120?

For the mathematicians and physicists problem of amritapuri region we did dp ( very similar to this problem), but got mle even after replacing 2 d input array by a map of pairs.Any suggestions?

Thank you.

How to solve The number of good subarrays

For each L you can find the smallest R by binary search and if L,R is good then L,(R+1) is also good.

Could you please elaborate your checker function of binary search

So for checking if a subarray is good after removing [l,r] you need to count the f(rem) array, for that you can take the contribution of each bit for example if ith bit is set in k subarrays then the contribution will be 2^i*k for finding the number of subarray that has ith bit set you can do is total_subarray-number_of_subarrays_where_ith_bit_is_off. For achieving this you can keep some prefix suffix arrays.

Refer this code for solution: here

PS: Sorry for my alien language :(

Thank you

Kanpur-Mathura Online Qualifier Round unofficial list here. (made by me :))

What are the numbers next to the college name? The number of teams qualifying?

Nope, they're just the count, stating the no of times that college is present in under 100.

is the selection criteria for kanpur-mathura regionals same as amritapuri regionals? Like do they too 1st select the top team from every other colleges?

Our team has rank 45 from Kanpur-Mathura and we are the 2nd team from our college and the 1st team has rank 10 so do we stand a chance for regionals

Yes, ofc!

If one team is selected from a college, 2nd team wouldn't be allowed, right ?

That is the rule for Amritapuri regionals, not Mathura regionals. You can check last year's criteria here.

I can't believe that such a great singer is on Codeforces. I am your big fan.

Are qualification rules for Amritapuri same as last year? Can more than 3 teams qualify from an institute?

Any ideas as to when the results would be announced? As the regional dates are close approaching, and most of us would need to book flights to get to Bangalore/Amritapuri.

Results for Amritapuri have been announced: link

gwalior pune region info anyone

We got 180 rank. Is it good for qualifying mathura site!

Depends upon the no. of slots :)

When will mathura region results gonna be declare?

today or tomorrow, there are 150 seats

Source — codedrills telegram channel

(someone claimed to got reply from icpc mathura-kanpur via email )

The guy who said on telegram : "Source: Trust me bro"

150 seats, r u serious?? Haha, According to Kanpur max to max 70-80 seats.

Yeah the seats in kanpur will be 70-80 but the combined seats of kanpur mathura should be atleast 130

It's not a combined regional site. It's only Mathura where the regionals are going to be held as per my knowledge.

Actually it's clearly mentioned on the icpc kanpur-mathura page that the contest is jointly hosted by GLA University,Mathura and CSJM University,Kanpur.

Ohh! Thank you for the info.

Selected teams for kanpur — mathura No. of slots = 150

can someone share official telegram link for mathura regionals?

+1

Is there any telegram group for individual regionals?