No.2598 Kadomatsu on Tree
タグ : / 解いたユーザー数 27
作問者 :
Problem Statement
For an integer sequence $a=(a_1,a_2,\dots,a_n)$ of length $n$, its Kadomatsu degree is defined as the number of $i$ that are at least $2$ and less than $n$ and satisfy the following condition.
- At least one of "$a_i< a_{i+1}$ and $a_i< a_{i-1}$" or "$a_i> a_{i+1}$ and $a_i> a_{i-1}$" holds.
Here, the Kadomatsu degree of any integer sequence of length at most $2$ is defined to be $0$.
There is a simple connected undirected graph with $N$ vertices and $N-1$ edges. The vertices are numbered $1,2,\dots,N$, and the $i$-th edge connects vertex $U_i$ and vertex $V_i$ bidirectionally.
You are also given an integer sequence $A$ of length $N$.
Let $f(i,j)$ be the Kadomatsu degree of $q$, where $q=(A_{p_1},A_{p_2},\dots,A_{p_n})$ is obtained from the unique integer sequence $p=(p_1,p_2,\dots,p_n)$ of length $n$ satisfying all of the following conditions.
- $p_1=i$
- $p_n=j$
- $1\leq p_k\leq N(1\leq k\leq n)$
- All elements of $p$ are distinct.
- For every $k$ at least $1$ and less than $n$, vertex $p_k$ and vertex $p_{k+1}$ are directly connected by an edge.
Find $\sum_{i=1}^{N}\sum_{j=i}^{N}f(i,j)$ modulo $998244353$.
Input
$N$
$U_1\ V_1$
$U_2\ V_2$
$\vdots$
$U_{N-1}\ V_{N-1}$
$A_1\ A_2\ \dots\ A_N$
- $3\leq N\leq 2\times 10^5$
- $1\leq U_i,V_i\leq N(1\leq i\leq N-1)$
- The given graph is connected.
- $1\leq A_i\leq 10^9$
Output
Print the answer on $1$ line.
Sample
Sample 1
Input
5 1 3 2 1 4 1 4 5 2 1 3 1 2
Output
5
The cases where $f(i,j)$ is at least $1$ are shown below.
- $f(1,5)=1\dots p=(1,4,5),q=(2,1,2)$, and the Kadomatsu degree of $q$ is $1$
- $f(2,4)=1\dots p=(2,1,4),q=(1,2,1)$, and the Kadomatsu degree of $q$ is $1$
- $f(2,5)=2\dots p=(2,1,4,5),q=(1,2,1,2)$, and the Kadomatsu degree of $q$ is $2$
- $f(3,5)=1\dots p=(3,1,4,5),q=(3,2,1,2)$, and the Kadomatsu degree of $q$ is $1$
Therefore, the answer is $5$.
Sample 2
Input
6 1 2 2 3 1 5 5 6 4 5 1 1 1 1 1 1
Output
0
Sample 3
Input
10 6 8 6 1 5 10 5 2 6 4 2 4 5 9 8 7 3 9 461924924 987491630 891274602 524053807 460183912 97638725 932784974 244569286 453506405 44117081
Output
50
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