QOJ.ac

QOJ

実行時間制限: 2.0 s メモリ制限: 1024 MB 満点: 100

#9477. 拓扑排序

統計

给定一个正整数 $N$ 和一个 $(1, 2, \dots, N)$ 的排列 $P = (P_1, P_2, \dots, P_N)$。

求满足以下条件的、顶点标号为 $1, 2, \dots, N$ 且边无标号的有向图的数量:

  • 该图是一个简单有向无环图(DAG)。即它不包含有向环,也不包含重边。
  • 该图的字典序最小的拓扑排序为 $P$。

输出答案对 $998244353$ 取模的结果。

输入格式

输入通过标准输入给出,格式如下:

$N$ $P_1 \ P_2 \ \dots \ P_N$

  • $2 \le N \le 2 \times 10^5$
  • $(P_1, P_2, \dots, P_N)$ 是 $(1, 2, \dots, N)$ 的一个排列。
  • 所有输入值均为整数。

输出格式

输出一行答案。

样例

输入格式 1

3
1 3 2

输出格式 1

4

说明

在第一个样例中,以下四个有向图满足条件:

输入格式 2

5
1 2 3 4 5

输出格式 2

1024

输入格式 3

6
4 2 1 5 6 3

输出格式 3

4096

Discussions

About Discussions

The discussion section is only for posting: General Discussions (problem-solving strategies, alternative approaches), and Off-topic conversations.

This is NOT for reporting issues! If you want to report bugs or errors, please use the Issues section below.

Open Discussions 0
No discussions in this category.

Issues

About Issues

If you find any issues with the problem (statement, scoring, time/memory limits, test cases, etc.), you may submit an issue here. A problem moderator will review your issue.

Guidelines:

  1. This is not a place to publish discussions, editorials, or requests to debug your code. Issues are only visible to you and problem moderators.
  2. Do not submit duplicated issues.
  3. Issues must be filed in English or Chinese only.
Active Issues 0
No issues in this category.
Closed/Resolved Issues 0
No issues in this category.