题目描述
Problem Statement
You are given a simple connected undirected graph G with N vertices and M edges.
The vertices of G are numbered vertex $1, vertex 2, \ldots$, and vertex N, and its edges are numbered edge $1, edge 2, \ldots$, and edge M.
Edge i connects vertex U_i and vertex V_i.
You are also given a subset of the edges: S=${x_1,x_2,\ldots,x_K$}.
Determine if there is a walk on G that contains edge x exactly once for all $x \in$ S.
The walk may contain an edge not in S any number of times (possibly zero).
What is a walk?
A walk on an undirected graph G is a sequence consisting of k vertices (k is a positive integer) and $(k-1) edges occurring alternately, v_1,e_1,v_2,\ldots,v_{k-1},e_{k-1},v_k$, such that
edge e_i connects vertex v_i and vertex v_{i+1}. The sequence may contain the same edge or vertex multiple times.
A walk is said to contain an edge x exactly once if and only if there is exactly one $1\leq i\leq k-1$ such that e_i=x.
Input
The input is given from Standard Input in the following format:
N M
U_1 V_1
U_2 V_2
$\vdots$
U_M V_M
K
$x_1 x_2 \ldots x_K$
Output
Print Yes if there is a walk satisfying the condition in the Problem Statement; print No otherwise.
Constraints
- $2 \leq N \leq 2\times 10^5$
- $N-1 \leq M \leq \min(\frac{N(N-1)}{2},2\times 10^5)$
- $1 \leq U_i<V_i\leq N$
- If $i\neq j$, then $(U_i,V_i)\neq (U_j,V_j)$ .
- G is connected.
- $1 \leq K \leq M$
- $1 \leq x_1<x_2<\cdots<x_K \leq M$
- All values in the input are integers.
Sample Input 1
6 6
1 3
2 3
3 4
4 5
4 6
5 6
4
1 2 4 5
Sample Output 1
Yes
The walk (v_1,e_1,v_3,e_3,v_4,e_4,v_5,e_6,v_6,e_5,v_4,e_3,v_3,e_2,v_2) satisfies the condition, where v_i denotes vertex i and e_i denotes edge i.
In other words, the walk travels the vertices on G in this order: $1\to$ $3\to$ $4\to$ $5\to$ $6\to$ $4\to$ $3\to$ 2.
This walk satisfies the condition because it contains edges 1, 2, 4, and 5 exactly once each.
Sample Input 2
6 5
1 2
1 3
1 4
1 5
1 6
3
1 2 3
Sample Output 2
No
There is no walk that contains edges 1, 2, and 3 exactly once each, so No should be printed.
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分