I solved ABD!!!!!!!!!!!!!!!OHHHHHHHHHHHHHHHHHHH I think D is easier than B,C(mabe easierthanA??),and luckyly, I read D ,very surprise

Am I doing ARC or a stupid guessing game?

I want to know how many participant pieced together the answer to Problem E after solving Problem D

How mysterious!I came up with a LCT solution for Problem C.

The repeated question and the strange guessing question... E was indeed interesting, but adding D made the bias in this 5-question round too obvious. I think this was the worst ARC round I've ever seen.

Too many guesses

The Problem D and E should be placed in April Fool Contest

Trash contest. ABDE are all conclusion-based problems and C is an unoriginal problem.

https://www.luogu.com.cn/problem/P3623

While working on D, I had discovered a relation between the answers to D and E (At first I was thinking about inversion numbers), but after solving D by intuition, I didn't notice about that and couldn't solve E. I'm sad

I have solved questions A to D, and I believe that these three questions ABD should not be placed in the same competition.

And why is C almost the same as one of the questions in APIO2008?

I have no idea how to come up with the core observation in problem D, so can this problem be solved without guessing the expression for the answer right from the start?

I was misbanned, pls unban my AtCoder account leo120306, thank you. Perhaps the reason why I was banned is that the code for question A did not use my usual template. Here I would like to explain: When I was about to write the code for question A, my IDE happened to have a simple template, and the code for question A was not complicated, so I wrote it directly on this basis. I apologize for the extra workload.

My code for A:

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

constexpr int N=505;
int n,q,a[N][N],s[]={0,2,4,1,3};
int main(){
	ios::sync_with_stdio(0);cin.tie(0);
	cin>>n;
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
			cin>>a[i][j],cout<<s[a[i][j]]<<" \n"[j==n];
	
	return 0;
}

The details match my habits instead of AI's.

I solved C, but not A and B — I think tackling AB this time could really help me. (but… how come more people passed D than C?)

Bad.

AtCoder please unban TH911.

I can promise that I didn't use AI to help me solve the problemsin arc225,and I was banned for mistake.

Maybe I ought to explain my code?

In the problem B,I used vector because I had gussed the solution and I was wrong.Then when I thought of a real solution,I directly modify my old code.

In the problem C,I packed a struct called dsu.

struct dsu{
	int f[N+1],size[N+1];
	
	int find(int x){
		if(f[x]!=x){
			return f[x]=find(f[x]);
		}
		return x;
	}
	void merge(int x,int y){
		x=find(x),y=find(y);
		if(size[x]<size[y]){
			f[x]=y;
			size[y]+=size[x];
		}else{
			f[y]=x;
			size[y]+=size[x];
		}
	}
	void build(int n){
		for(int i=1;i<=n;i++){
			f[i]=i;
		}
	}
}dsu;

It's just my habit,perhaps you could find it out at https://www.cnblogs.com/TH911/p/-/P12479(my blog)or luogu R230197990.Actually,my dsu is not fully correct in the code for problem C.

And last,as a Chinese stident,the time of the contests of CodeForces isn't so comfotable for me.So my rating isn't so high,and perhaps you won't believe me.But still,I do believe you're understanding.

Thanks for your listening.

I remembered my code in the last few hours,and I submitted them by another account.

Them can be seen at the summissions.

Maybe the code for the problem C is a little different from my original code of the account TH911.

The data range limit of $$$2 \le n \le 500$$$ for Problem A is so misleading. The intended solution is actually an $$$O(n^2)$$$ construction, but this range makes you think it's an $$$O(n^3)$$$ one. I wasted an hour on this problem.

I think they shouldn't put so many conclusion or Ad-hoc problems into one contest.This will cause the contest to distinguish contestants in a random manner.