反转排列AI (CI翻译)
Problem Statement
题目描述
AI (CI翻译)You are given an integer $N$ and a permutation $P=(P_1,P_2,\ldots,P_N)$ of $(1,2,\ldots,N)$.
给定一个整数 $N$ 和一个 $(1,2,\ldots,N)$ 的排列 $P=(P_1,P_2,\ldots,P_N)$。AI (CI翻译)
For a permutation $Q=(Q_1,Q_2,\ldots,Q_N)$ of $(1,2,\ldots,N)$, let $Q'=(Q_1',Q_2',\ldots,Q_N')$ be the lexicographically smallest permutation obtainable by performing the following operation exactly once:
对于一个 $(1,2,\ldots,N)$ 的排列 $Q=(Q_1,Q_2,\ldots,Q_N)$,令 $Q'=(Q_1',Q_2',\ldots,Q_N')$ 表示恰好进行一次以下操作后能够得到的字典序最小的排列:AI (CI翻译)
- Choose a pair of integers
$(l,r)$satisfying$1\le l\le r\le N$, and reverse$Q_l,Q_{l+1},\ldots,Q_r$. More precisely, replace$Q$with$(Q_1,Q_2,\ldots,Q_{l-1},Q_r,Q_{r-1},\ldots,Q_l,Q_{r+1},Q_{r+2},\ldots,Q_N)$.
- 选择一对满足
$1\le l\le r\le N$的整数$(l,r)$,将$Q_l,Q_{l+1},\ldots,Q_r$反转。更具体地说,将$Q$替换为$(Q_1,Q_2,\ldots,Q_{l-1},Q_r,Q_{r-1},\ldots,Q_l,Q_{r+1},Q_{r+2},\ldots,Q_N)$。
Find the number, modulo $998244353$, of permutations $Q$ of $(1,2,\ldots,N)$ such that $Q'=P$.
求满足 $Q'=P$ 的 $(1,2,\ldots,N)$ 的排列 $Q$ 的数量。答案对 $998244353$ 取模。AI (CI翻译)
You are given $T$ test cases; solve each of them.
给定 $T$ 组测试数据,请分别求出每组测试数据的答案。AI (CI翻译)
Constraints
约束条件
AI (CI翻译)$1\le T$$1\le N\le 5\times 10^5$$P$is a permutation of$(1,2,\ldots,N)$.- The sum of
$N$over all test cases is at most$5\times 10^5$. - All input values are integers.
$1\le T$$1\le N\le 5\times 10^5$$P$是一个$(1,2,\ldots,N)$的排列。- 所有测试数据的
$N$之和不超过$5\times 10^5$。 - 所有输入值均为整数。
Input
输入格式
AI (CI翻译)The input is given from Standard Input in the following format:
输入从标准输入中按以下格式给出:AI (CI翻译)
T
\text{case}_1
\text{case}_2
\vdots
\text{case}_T
T
\text{case}_1
\text{case}_2
\vdots
\text{case}_TAI (CI翻译)
Each test case is given in the following format:
每组测试数据按以下格式给出:AI (CI翻译)
N
P_1 P_2 \ldots P_N
N
P_1 P_2 \ldots P_NAI (CI翻译)
Output
输出格式
AI (CI翻译)Output the answers for the test cases in order, separated by newlines.
按顺序输出各组测试数据的答案,每个答案占一行。AI (CI翻译)
样例
4
3
1 3 2
1
1
4
4 3 2 1
6
1 2 6 4 5 3
2
1
0
9
题面与样例版权归 AtCoder 及出题人所有;中文翻译由 AI 生成(gpt-6.1-sol),如有出入请以原文为准。