Hello everybody!

Today, Codeforces Round #137 for the Second Division Participants will take place. As usual, all other interested persons can take part in it.

The problems have been developed by a group of authors from Vladivostok: Ilya Zban (izban), Alexey Evsyukov (aevsyukov), Zakhar Voit (zakharvoit).

Gerald Agapov (Gerald) has greatly contributed as well and we thank him for it. The translation of the problems has been done by Maria Belova (Delinur) — thanks to her! We are also grateful to Pavel Kunyavskiy (PavelKunyavskiy), who has help us in the preparation of the contest.

We hope you will have fun and like this round. The points distribution will be standard (500 — 1000 — 1500 — 2000 — 2500).

Good luck to everybody!

UPD: The start will be 15 minutes later due to technical reasons, we apologize.

UPD2: Congratulation to winners!

In second division:

1: zxl0714

2: resodo

3: mugurelionut

5: CCC

7: loveSakura

8: siralop

9: yuxingdubai

10: b821213

In first division:

1: navi

2: Shik

3: SteamTurbine

UPD3: The editorial is published.

I am a novice and competing first time on codeforces. Can you please guide me through the blueprints of competition process. Thanks for your help in advance!

You can read FAQ(http://www.codeforces.com/help) or write a virtual contest

Good Luck & Have Fun :)

thanks

Codeforces servers went owie. :(

Let's hope in short and clear statements :)

Eat lunch as fast as you can... and wait 12minutes for contest start :D

Life is evil :)

What's the trouble before?

Can someone explain test 1 on div2 C problem? Why is it: 2 3 2 1 1 1 1 and not for example: 1 1 2 1

Codeforces rules forbid asking about problems during the contest.

It is related to the clarity of the test case , I think, but nvm :)

You can ask on the contest page

I can't understand problem C and D mean. :|

Could anyone give me an Idea for solving C without having to decompose all the values to its prime factors (this strategy gave me TLE)? Or is it mandatory to do that and my implemtation was simply too slow?

Are You using Eratostenes sieve or naive approach?

When I finally did dare to lock my C, I found that I can hack 2 solutions with max tests, then the contest ended. Sigh. Seems courage is really important.

There was a slight error in the problem description. The "Input" says columns will be given first then the rows. However, the examples showed that this was not the case. Anyway, the round was good.

Thanks you.

Very long systest.

I feel there was not a need for so many test cases for Problem B. Perhaps that is why systests are slow.

Yes it's very slow. Now it reach the first hour submission in one hour to.

Reds( http://www.codeforces.com/contest/222/submission/2109757 ) can also fail div-2's A. Well done problem setters! :)

Is there a particular reason why the two pointer solution gives TLE when using library sort in Java but gives AC when using library sort in C++? Is it Java I/O or the library sort? I see that uwi has an AC Java solution using radix sort, but I am yet to see an AC Java solution using Arrays.sort.

google "java sort hack site:codeforces.com".

in a nutshell:

int[] a; Arrays.sort(a); // — N^2 operations

Integer[] a; Arrays.sort(a); // — N Log N operations

The root of this problem is that Java uses mergesort to sort Reference types and qsort to sort Basic types. So simple anti-qsort test can fail all your attempts when you sort int[] instead of Integer[]

So, stupid of me! This cost me E. Wasted too much time on A, so didn't had time to debug :(. Anyway, I feel happy that my approach was correct.

It was a good problem set. Thanks!

I think the problems in this contest is so simple that too many people killed all the problems :(

Hi, I have a question on test 8 of Problem D. The test is : 10 5

3 1 1 2 1 3 1 1 2 3

2 1 3 2 1 3 3 3 3 1

If we sort the array we will get: 6 5 5 4 4 4 4 4 2 2 So isn't the worst place is 3 ? But the answer is 5, i don't get this.

You arrange the resulting array in not optimal way.

It's possible to do so: (3 + 3) (3 + 3) (3 + 2) (3 + 2) (3 + 2) ...

and our guy has 5 points, so he's on the 5th place.

Thank you a lot.

My bad. I thought 1 column is the points of 1 person.

In second example testcase from problem statement you could see that this is not true :P

user editorial for the round please?

It's coming soon.

Can someone please explain the correctness of C problem. Actually I understood the approach, but i am not able to figure out why it will work Thanks.