All construction problems. The construction problems test the thinking ability and IQ the most. But the problem is that I'm not good at both of it. I'm 蒟蒻.

Ugh. Question D number theory can't do it. Question F can even be failed in a two-way linked list... I feel that my thinking ability is indeed not able to keep up.

## A. Nezzar and Colorful Balls

### Solution

Just count the number with the most occurrences.

## B. Nezzar and Lucky Number

Interesting construction problem. Get 1 TLE because of typo error.

Also checked official solution. But not very clear about it. Personally think my solution is more simple and clear. But anyway, it's problem B, there can be lots of different solutions. Nothing special.

## C. Nezzar and Symmetric Array

Not note requires int64 for the input. Get one RE.

Also refer to the description of problem. $a$ should include distinct integers. I forgot this one once. Get WA7 for this.

## D. Nezzar and Board

Number theory. Bézout's lemma. Don't know this one.

## E. Nezzar and Binary String

Still can handle segment tree very smoothly. Want start with $s$ first. But it's too complex to do. So turn to start from $f$. Then it much easier to solve.

## F. Nezzar and Nice Beatmap

I'm too stupid to implement two-way linked list correctly. T7 and WA7 because of it. I realize this until I add a exception below:

int ans = n;
Point now = last;
while (now != null) {
now.ans = ans;
ans--;
now = now.pre;
}
//check if the two-way linked list is broken.
if (ans != 0) throw new RuntimeException();