CF1067E.Random Forest Rank
普及/提高-
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题目描述
Let's define rank of undirected graph as rank of its adjacency matrix in Rn×n .
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⋅2n−1 modulo 998244353 (it is easy to show that E⋅2n−1 is an integer).
输入格式
First line of input contains n ( 1≤n≤5⋅105 ) — number of vertices.
Next n−1 lines contains two integers u v ( 1≤u,v≤n;u=v ) — indices of vertices connected by edge.
It is guaranteed that given graph is a tree.
输出格式
Print one integer — answer to the problem.
输入输出样例
输入#1
3 1 2 2 3
输出#1
6
输入#2
4 1 2 1 3 1 4
输出#2
14
输入#3
4 1 2 2 3 3 4
输出#3
18