atcoder#ABC286G. [ABC286G] Unique Walk
[ABC286G] Unique Walk
Score : points
Problem Statement
You are given a simple connected undirected graph with vertices and edges. The vertices of are numbered vertex , vertex , , and vertex , and its edges are numbered edge , edge , , and edge . Edge connects vertex and vertex . You are also given a subset of the edges: .
Determine if there is a walk on that contains edge exactly once for all . The walk may contain an edge not in 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.Constraints
- $N-1 \leq M \leq \min(\frac{N(N-1)}{2},2\times 10^5)$
- $1 \leq U_i
- If , then .
- is connected.
- $1 \leq x_1
- All values in the input are integers.
Input
The input is given from Standard Input in the following format:
Output
Print Yes
if there is a walk satisfying the condition in the Problem Statement; print No
otherwise.
6 6
1 3
2 3
3 4
4 5
4 6
5 6
4
1 2 4 5
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 denotes vertex and denotes edge . In other words, the walk travels the vertices on in this order: . This walk satisfies the condition because it contains edges , , , and exactly once each.
6 5
1 2
1 3
1 4
1 5
1 6
3
1 2 3
No
There is no walk that contains edges , , and exactly once each, so No
should be printed.