Codeforces Round 518 (Div. 1) [Thanks, Mail.Ru!]
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Let's define rank of undirected graph as rank of its adjacency matrix in $\mathbb{R}^{n \times n}$.
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Given a tree. Each edge of this tree will be deleted with probability $1/2$, all these deletions are independent. Let $E$ be the expected rank of resulting forest. Find $E \cdot 2^{n-1}$ modulo $998244353$ (it is easy to show that $E \cdot 2^{n-1}$ is an integer).
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Input
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First line of input contains $n$ ($1 \le n \le 5 \cdot 10^{5}$) — number of vertices.
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Next $n-1$ lines contains two integers $u$ $v$ ($1 \le u, \,\, v \le n; \,\, u \ne v$) — indices of vertices connected by edge.
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It is guaranteed that given graph is a tree.
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Output
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Print one integer — answer to the problem.
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样例
Input #1
3
1 2
2 3
Output #1
6
InputCopy
OutputCopy
Input #2
4
1 2
1 3
1 4
Output #2
14
InputCopy
OutputCopy
Input #3
4
1 2
2 3
3 4
Output #3
18
InputCopy
OutputCopy
题目信息
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动态规划
图匹配
数学
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