题目描述
Problem Statement
There is a tree T with N vertices. The $i-th edge (1\leq i\leq N-1) connects vertex U_i$ and vertex V_i.
You are given two different vertices X and Y in T.
List all vertices along the simple path from vertex X to vertex Y in order, including endpoints.
It can be proved that, for any two different vertices a and b in a tree, there is a unique simple path from a to b.
What is a simple path?
For vertices X and Y in a graph G, a path from vertex X to vertex Y is a sequence of vertices $v_1,v_2, \ldots, v_k$ such that v_1=X, v_k=Y, and v_i and v_{i+1} are connected by an edge for each $1\leq i\leq k-1$.
Additionally, if all of $v_1,v_2, \ldots, v_k$ are distinct, the path is said to be a simple path from vertex X to vertex Y.
Input
The input is given from Standard Input in the following format:
N X Y
U_1 V_1
U_2 V_2
$\vdots$
U_{N-1} V_{N-1}
Output
Print the indices of all vertices along the simple path from vertex X to vertex Y in order, with spaces in between.
Constraints
- $1\leq N\leq 2\times 10^5$
- $1\leq X,Y\leq N$
- $X\neq Y$
- $1\leq U_i,V_i\leq N$
- All values in the input are integers.
- The given graph is a tree.
Sample Input 1
5 2 5
1 2
1 3
3 4
3 5
Sample Output 1
2 1 3 5
The tree T is shown below. The simple path from vertex 2 to vertex 5 is $2 \to$ $1 \to$ $3 \to$ 5.
Thus, 2,1,3,5 should be printed in this order, with spaces in between.
Sample Input 2
6 1 2
3 1
2 5
1 2
4 1
2 6
Sample Output 2
1 2
The tree T is shown below.
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分