题目描述
You have a tree with $n$ vertices, some of which are marked. A tree is a connected undirected graph without cycles.
Let $f_i$ denote the maximum distance from vertex $i$ to any of the marked vertices.
Your task is to find the minimum value of $f_i$ among all vertices.
For example, in the tree shown in the example, vertices $2$, $6$, and $7$ are marked. Then the array $f(i) = [2, 3, 2, 4, 4, 3, 3]$. The minimum $f_i$ is for vertices $1$ and $3$.
Input
The first line contains an integer $t$ ($1 \le t \le 10^4$) — the number of test cases.
The first line of each test case contains two integers $n$ and $k$ ($1 \le k \le n \le 2 \cdot 10^5$) — the number of vertices in the tree and the number of marked vertices, respectively.
The second line of each test case contains $k$ integers $a_i$ ($1 \le a_i \le n, a_{i-1} < a_i$) — the indices of the marked vertices.
The next $n - 1$ lines contain two integers $u_i$ and $v_i$ — the indices of vertices connected by the $i$-th edge.
It is guaranteed that the sum of $n$ over all test cases does not exceed $2 \cdot 10^5$.
Output
For each test case, output a single integer — the minimum value of $f_i$ among all vertices.
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分