AtCoder Beginner Contest 272
Ex
Flipping Coins 2
AtCoder
⌀ 3740
原题
←G →
翻译中…

Problem Statement

翻译中…

$N$ coins numbered $0,1,\ldots,N-1$ are arranged in a row. Initially, all coins are face up. Also, you are given a sequence $A$ of length $N$ consisting of integers between $0$ and $N-1$.

翻译中…

Snuke will choose a permutation $p=(p_1,p_2,\ldots,p_N)$ of $(1,\ldots,N)$ at equal probability and perform $N$ operations. In the $i$-th $(1\leq i \leq N)$ operation,

翻译中…
  • he flips $(A_{p_i}+1)$ coins: coin $(i-1) \bmod N$, coin $(i-1+1 ) \bmod N$, $\ldots$, and coin $(i -1+ A_{p_i}) \bmod N$.
翻译中…

After the $N$ operations, Snuke receives $k$ yen (the currency in Japan) from his mother, where $k$ is the number of face-up coins.

翻译中…

Find the expected value, modulo $998244353$, of the money Snuke will receive.

翻译中…

Definition of expected value modulo $998244353$ In this problem, we can prove that the sought expected value is always a rational number. Moreover, under the Constraints of this problem, when the sought expected value is represented as an irreducible fraction $\frac{y}{x}$, it is guaranteed that $x$ is indivisible by $998244353$. Then, an integer $z$ between $0$ and $998244352$ such that $xz \equiv y \pmod{998244353}$ is uniquely determined. Find such $z$.

翻译中…

Constraints

翻译中…
  • $1 \leq N\leq 2\times 10^5$
  • $0\leq A_i \leq N-1$
  • All values in the input are integers.
翻译中…

Input

翻译中…

The input is given from Standard Input in the following format:

翻译中…

N
A_1 A_2 \ldots A_N

翻译中…

Output

翻译中…

Print the answer.

翻译中…

样例

Input #1
2
0 1
Output #1
1
$p$ can be either $(1,2)$ or $(2,1)$. - If $(1,2)$ is chosen as $p$: In the first operation, coin $0$ is flipped, and in the second operation, coin $1$ and coin $0$ are flipped. One coin, coin $0$, results in being face up, so he receives $1$ yen. - If $(2,1)$ is chosen as $p$: In the first operation, coin $0$ and coin $1$ are flipped, and in the second operation, coin $1$ is flipped. One coin, coin $1$, results in being face up, so he receives $1$ yen. Therefore, the expected value of the money he receives is $1$ yen.
Input #2
4
3 1 1 2
Output #2
665496237
Print the expected value modulo $998244353$.
题目信息
题号
abc272_h
时间限制
10 s
内存限制
1024 MB

题面与样例版权归 AtCoder 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。