题目描述
Problem Statement
We have a tree T with vertices numbered 1 to N. The i-th edge of T connects vertex u_i and vertex v_i.
Let us use T to define the similarity of $a permutation P = (P_1,P_2,\ldots,P_N)$ of $(1,2,\ldots,N)$ as follows.
- For $a simple path x=(x_1,x_2,\ldots,x_k)$ in T, let $y=(P_{x_1}, P_{x_2},\ldots,P_{x_k})$. The similarity is the maximum possible length of a longest common subsequence of x and y.
Construct a permutation P with the minimum similarity.
What is a subsequence?
A subsequence of a sequence is a sequence obtained by removing zero or more elements from that sequence and concatenating the remaining elements without changing the relative order.
For instance, (10,30) is a subsequence of (10,20,30), but (20,10) is not.
What is a simple path?
For vertices X and Y in a graph G, a walk from X to Y is a sequence of vertices $v_1,v_2, \ldots, v_k$ such that v_1=X, v_k=Y, and there is an edge connecting v_i and v_{i+1}. A simple path (or simply a path) is a walk such that $v_1,v_2, \ldots, v_k$ are all different.
Input
The input is given from Standard Input in the following format:
N
u_1 v_1
u_2 v_2
$\vdots$
u_{N-1} v_{N-1}
Output
Print a permutation P with the minimum similarity, separated by spaces. If multiple solutions exist, you may print any of them.
Constraints
- $2 \leq N \leq 5000$
- $1\leq u_i,v_i\leq N$
- The given graph is a tree.
- All numbers in the input are integers.
Sample Input 1
3
1 2
2 3
Sample Output 1
3 2 1
This permutation has a similarity of 1, which can be computed as follows.
-
For x=(1), we have y=(P_1)=(3). The length of a longest common subsequence of x and y is 0.
-
For x=(2), we have y=(P_2)=(2). The length of a longest common subsequence of x and y is 1.
-
For x=(3), we have y=(P_2)=(1). The length of a longest common subsequence of x and y is 0.
-
For x=(1,2), we have y=(P_1,P_2)=(3,2). The length of a longest common subsequence of x and y is 1. The same goes for x=(2,1), the reversal of (1,2).
-
For x=(2,3), we have y=(P_2,P_3)=(2,1). The length of a longest common subsequence of x and y is 1. The same goes for x=(3,2), the reversal of (2,3).
-
For x=(1,2,3), we have y=(P_1,P_2,P_3)=(3,2,1). The length of a longest common subsequence of x and y is 1. The same goes for x=(3,2,1), the reversal of (1,2,3).
We can prove that no permutation has a similarity of 0 or less, so this permutation is a valid answer.
Sample Input 2
4
2 1
2 3
2 4
Sample Output 2
3 4 1 2
If multiple permutations have the minimum similarity, you may print any of them. For instance, you may also print 4 3 2 1.
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分