We will hold AtCoder Regular Contest 176.

- Contest URL: https://atcoder.jp/contests/arc176
- Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20240421T2100&p1=248
- Duration: 120 minutes
- Number of Tasks: 6
- Writer: PCTprobability
- Tester: maspy, Nyaan
- Rated range: — 2799

The point values will be 400-400-700-700-800-1000.

We are looking forward to your participation!

Hoping for the best ARC Round!

Good luck to all who are competing!

As a writer,I hope everyone who participates in this contest will enjoy it. Good luck!

Good Luck!Hope C!

I didn't get the question right

A was kinda tricky if you don't get the point :( I spent 30+ min on it :(

what was the idea?

can u please explain the solution of A. I am unable to get (b[i] — a[i] + n) % n , i cant understand it even after looking at the editorial

Maybe you can look at the following cases:

Where

`x`

and`y`

means $$$1$$$ and`o`

means $$$0$$$. You can divide them into $$$n$$$ sets that in each set, the elements has a same $$$(b_i-a_i)\bmod n$$$.Nice Explaination , thankyou so much

Yet another pure math contest. I suck at math, so dislike.

can B be solved using bitmasks? I don't know about it but i reduced it to a point like this where quotient is

but I was unable to solve it as I'm not good enough in bitmasks and stuff

what is the idea behind A?

Does B have no testcase with $$$n = m-1$$$ and $$$k=m-1$$$? I realised this condition a few seconds after submitting, but to my surprise, my code got AC.

Data of problem A is weak. As a result of me and my friends' verification, there is not a single piece of data that is $$$M \ne N < 2M$$$. And this is the evidence.

For example, this code which I submitted during the contest must be wrong. It gives completely wrong answer with this input.

I sent a clarification an hour ago, and I'll update as soon as possible when I see any response. I hope that I can write up a code that will allow me to get Accepted after the data is strengthened.

And I LOVE problem B. Very beautiful problem!

can anyone explain question b solution i did not understand

My First ARC got a 0pts but Rating+26, seems like it does need so many brainstroming instead of a number of algorithms at ahead problems.

Problem B is really a clever problem. I think I will never notice the case k=m-1 until I read the editorials. Hats off to the problem writers!

Data of problem C is also weak

The Editorial of C says:

and I forgot to check this case ($$$X_v < k$$$) during the contest, but my code got AC.

There is an input for this case:

my code during contest will give $$$40320$$$.

My code passed your case, but for this case:

my code will give

4.I'm not sure whether this is common.

I hacked a lot people when I try to use their codes to check my wrong code. I'm so helpless. Who could help me?

Can someone explain the following code for problem A — 01 Matrix Again ?

There are total of n^2 elements in matrix so each (i-j)%n will occur atmost n times.

(you can draw the matrix of (i-j)%n for some n to see it youself)

since element are occurring on separate row and col we can assign 1 to such element that will increase the sum by n. How many times we need to do this? m times

So at last we just need to select m remainders out of n and assign 1 to those positions.

since some pairs are already given, we can just use remainder of those.

I hope it helps...

can someone explain me the problem problem D in it ,I cant understand how transition states are made.