A12254. Random Forest Rank
编程题
普及/提高-
知识点
题目描述
Let's define rank of undirected graph as rank of its adjacency matrix in $\mathbb{R}^{n \times n}$ .
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 $E \cdot 2^{n-1}$ modulo $998244353$ (it is easy to show that $E \cdot 2^{n-1}$ is an integer).
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).
输入格式
First line of input contains $n$ ( $1 \le n \le 5 \cdot 10^{5}$ ) — number of vertices.
Next $n-1$ lines contains two integers $u$ $v$ ( $1 \le u, \,\, v \le n; \,\, u \ne v$ ) — indices of vertices connected by edge.
It is guaranteed that given graph is a tree.
Next $n-1$ lines contains two integers $u$ $v$ ( $1 \le u, \,\, v \le n; \,\, u \ne v$ ) — 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