AtCoder Grand Contest 070
E
Remove 2K+1 Edges
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Problem Statement

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You are given positive integers $N$ and $K$. Consider an undirected tree $T$ with $(2K + 1)N + 1$ vertices labeled from $1$ to $(2K + 1)N + 1$. Among all such trees, find the number, modulo $998244353$, of trees that satisfy the following condition.

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  • It is possible to remove all edges from $T$ by repeating the following operation:
  • Choose a path of length $2K + 1$ and remove all edges in it. Formally, choose a sequence of distinct vertices $v_0, v_1, \dots, v_{2K+1}$ such that there exists an edge $(v_i, v_{i+1})$ for all $i$ such that $0 \leq i \leq 2K$, and remove the edge $(v_i, v_{i+1})$ for all $i$ such that $0 \leq i \leq 2K$.
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Constraints

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  • $1 \leq N \leq 1.3 \times 10^5$
  • $1 \leq K \leq 50$
  • All input values are integers.
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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 K

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Output

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Print the number, modulo $998244353$, of trees with $(2K + 1)N + 1$ vertices satisfying the condition.

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样例

Input #1
2 1
Output #1
8820
For example, consider a tree with edges $(1, 2)$, $(2, 3)$, $(2, 4)$, $(2, 6)$, $(3, 7)$, and $(4, 5)$. By doing the following steps, one can remove all edges from the tree, so it satisfies the condition in the problem statement: - Choose the path $(1,2,4,5)$ and remove edges $(1,2)$, $(2,4)$, $(4,5)$. - Choose the path $(6,2,3,7)$ and remove edges $(6,2)$, $(2,3)$, $(3,7)$. ![image](https://img.atcoder.jp/agc070/97f1043f2e834a849e1e3d10921cfb9b.png) There are $8820$ such trees in total.
Input #2
70 1
Output #2
273892456
Remember to print the count modulo $998244353$.
Input #3
12 29
Output #3
898069699
Input #4
100000 50
Output #4
158600909
题目信息
题号
agc070_e
时间限制
12 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。