AtCoder Regular Contest 114
B
Special Subsets
AtCoder
⌀ 1000
原题
← AC →
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Problem Statement

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Let $S$ be a set composed of all integers from $1$ through $N$.

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$f$ is a function from $S$ to $S$. You are given the values $f(1), f(2), \cdots, f(N)$ as $f_1, f_2, \cdots, f_N$.

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Find the number, modulo $998244353$, of non-empty subsets $T$ of $S$ satisfying both of the following conditions:

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  • For every $a \in T$, $f(a) \in T$.
  • For every $a, b \in T$, $f(a) \neq f(b)$ if $a \neq b$.
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Constraints

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  • $1 \leq N \leq 2 \times 10^5$
  • $1 \leq f_i \leq N$
  • All values in input are integers.
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Input

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Input is given from Standard Input in the following format:

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N
f_1 f_2 \ldots f_N

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Output

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Print the number of non-empty subsets of $S$ satisfying both of the conditions, modulo $998244353$.

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样例

Input #1
2
2 1
Output #1
1
We have $f(1) = 2, f(2) = 1$. Since $f(1) \neq f(2)$, the second condition is always satisfied, but the first condition requires $T$ to contain $1$ and $2$ simultaneously.
Input #2
2
1 1
Output #2
1
We have $f(1) = f(2) = 1$. The first condition requires $T$ to contain $1$, and the second condition forbids $T$ to contain $2$.
Input #3
3
1 2 3
Output #3
7
We have $f(1) = 1, f(2) = 2, f(3) = 3$. Both of the conditions are always satisfied, so all non-empty subsets of $T$ count.
题目信息
题号
arc114_b
时间限制
2 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。