Invitation to CodeChef Starters 153 (Rated upto 5 stars) - 25th September

We invite you to participate in CodeChef’s Starters 153, this Wednesday, 25th September, rated up to 5 stars (i.e. for users with a rating < 2200)

Time: 8:00 PM — 10:00 PM IST

Joining us on the problem setting panel are:

Written editorials will be available for all on discuss.codechef.com. Pro users can find the editorials directly on the problem pages after the contest. The video editorials of the problems will be available only to Pro users.

Also, if you have some original and engaging problem ideas, and you’re interested in them being used in CodeChef’s contests, you can share them here.
Hope to see you participating.

Good Luck!

1 Like

What the hell is going on with the contests

In today’s contest i submitted my 3rd Q (Another game ) in div3 at 25th minute
when around 250 submissions were there in div3 of this Q. And then i gone for study for my midsem paper tomorrow. I thought rating would increase because i submitted way earlier than all those cheaters out there, it increased initially but after some time i saw it dropped drastically , it literally came down to the point where i started, also i hadn’t done any wrong submissions thereafter. Why is it happening? What’s the point of doing these much and at the end rating won’t increase because of the cheaters.
Before contest:1485
After contest:1494
just a delta of +9 !! so demotivating
I saw there are telegram groups and whatsapp groups that are flooded with the solutions of the contest. In today’s time if someone genuinely thinks and solves questions their rating won’t gonna increase.
what should i do ,shall i stop giving contest ?? Otherwise every time this is going to happen!!

5 Likes

Its a shame that close to 7k Submissions are verdicted as TLE (Xometry (Easy Version) Practice Problem Solution Submissions), for Xometry (Easy Version) question, when most of the solutions are in expected time complexity

2 Likes

expected time complexity was O(n^2) without constant factors of unordered sets and maps, basically 5000*5000 is alot and one has to be careful.

Any idea what other optimizations were needed to make it strictly O(n^2), I did only O(n^2) XORs ignoring constant of unordered map but still got TLE
https://www.codechef.com/viewsolution/1093270103

unordered_map<int, int> cnt;
you are clearly using unordered_map<int,int>

Sorry I misunderstood your previous statement that it was expected to not use unordered set, but still curious why creating an array of size 10^6 for each test case passes when it is clear that T <= 1000
https://www.codechef.com/viewsolution/1093285133

1 Like

Here is one of the solutions published by editor CodeChef: Practical coding for everyone
its same as what I’ve done here CodeChef: Practical coding for everyone
I’ve also tried with both map<int,int> and unordered_map, and both gave TLE.

I’m fine if only only using predefined int array of size 1e6+1 gives AC and everyone who uses a map/unordered_map gets TLE.
but some getting AC and some others getting TLE while using map/unordered_map is unfair (including the above solution which the editor has published)

well it shouldn’t AC. i don’t know why. maybe bad tests?

It seems the second test, which took 0.24 seconds, was likely meant to handle this case. However, 250 * 2 * 10^6 might just fit within the limit due to efficient caching and compiler optimizations. I’m not entirely sure though, so take this with a grain of salt.

try to submit editor’s code it will give TLE.

Some solutions accepted using map .
I copy the submission and give now it also give tle

Then they could’ve set 10^3 as the upper bound for N. Imo, 5 \cdot 10^3 is too harsh for Starters.