A11283 | Andrey's Tree

Master Andrey loves trees $^{\dagger}$ very much, so he has a tree consisting of $n$ vertices.

But it's not that simple. Master Timofey decided to steal one vertex from the tree. If Timofey stole vertex $v$ from the tree, then vertex $v$ and all edges with one end at vertex $v$ are removed from the tree, while the numbers of other vertices remain unchanged. To prevent Andrey from getting upset, Timofey decided to make the resulting graph a tree again. To do this, he can add edges between any vertices $a$ and $b$ , but when adding such an edge, he must pay $|a - b|$ coins to the Master's Assistance Center.

Note that the resulting tree does not contain vertex $v$ .

Timofey has not yet decided which vertex $v$ he will remove from the tree, so he wants to know for each vertex $1 \leq v \leq n$ , the minimum number of coins needed to be spent to make the graph a tree again after removing vertex $v$ , as well as which edges need to be added.

$^{\dagger}$ A tree is an undirected connected graph without cycles.

Each test consists of multiple test cases. The first line contains a single integer $t$ ( $1 \le t \le 10^4$ ) — the number of test cases. The description of the test cases follows.

The first line of each test case contains a single integer $n$ ( $5 \le n \le 2\cdot10^5$ ) — the number of vertices in Andrey's tree.

The next $n - 1$ lines contain a description of the tree's edges. The $i$ -th of these lines contains two integers $u_i$ and $v_i$ ( $1 \le u_i, v_i \le n$ ) — the numbers of vertices connected by the $i$ -th edge.

It is guaranteed that the given edges form a tree.

It is guaranteed that the sum of $n$ over all test cases does not exceed $2\cdot10^5$ .

For each test case, output the answer in the following format:

For each vertex $v$ (in the order from $1$ to $n$ ), in the first line output two integers $w$ and $m$ — the minimum number of coins that need to be spent to make the graph a tree again after removing vertex $v$ , and the number of added edges.

Then output $m$ lines, each containing two integers $a$ and $b$ ( $1 \le a, b \le n, a \ne v, b \ne v$ , $a \ne b$ ) — the ends of the added edge.

If there are multiple ways to add edges, you can output any solution with the minimum cost.