AtCoder Beginner Contest 180
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Problem Statement
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Find the number of graphs with $N$ labeled vertices and $M$ unlabeled edges, not necessarily simple or connected, that satisfy the following conditions, modulo $(10^9+7)$:
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- There is no self-loop;
- The degree of every vertex is at most
$2$; - The maximum of the sizes of the connected components is exactly
$L$.
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Constraints
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$2 \leq N \leq 300$$1\leq M \leq N$$1 \leq L \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 M L
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Output
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Print the answer.
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样例
Input #1
3 2 3
Output #1
3
When the vertices are labeled $1$ through $N$, the following three graphs satisfy the condition:
- The graph with edges $1-2$ and $2-3$;
- The graph with edges $1-2$ and $1-3$;
- The graph with edges $1-3$ and $2-3$.
Input #2
4 3 2
Output #2
6
Input #3
300 290 140
Output #3
211917445
题目信息
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。