AtCoder Regular Contest 163
D
Sum of SCC
AtCoder
⌀ 2581
原题
← CE →
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Problem Statement

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Consider a directed graph $G$ with $N$ vertices numbered $1$ to $N$ that satisfies all of the following conditions.

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  • $G$ is a tournament. In other words, $G$ has no multi-edges or self-loops, and for any two vertices $u,v$ of $G$, exactly one of the edges $u \rightarrow v$ and $v \rightarrow u$ exists.
  • Among the edges of $G$, exactly $M$ are directed from a vertex with a smaller number to a vertex with a larger number.
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Find the total number of strongly connected components over all such directed graphs $G$, modulo $998244353$.

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Constraints

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  • $1 \le N \le 30$
  • $0 \le M \le \frac{N(N-1)}{2}$
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Input

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

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N M

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Output

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Print the answer.

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样例

Input #1
3 1
Output #1
7
Below are the three directed graphs $G$ that satisfy the conditions. The numbers of their strongly connected components are $3,1,3$ from left to right, so the answer is $7$. ![image](https://img.atcoder.jp/arc163/ee8acabc2a7d48164b3cc568e88f0840.png)
Input #2
6 2
Output #2
300
Input #3
25 156
Output #3
902739687
题目信息
题号
arc163_d
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。