P24592 [AtCoder] Typical Path Problem
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题目描述

Problem Statement

You are given a simple connected undirected graph G with N vertices and M edges.
The vertices and edges of G are numbered as vertex $1, vertex 2, \ldots, vertex N$, and edge $1, edge 2, \ldots, edge M,$ respectively, and edge $i (1\leq i\leq M) connects vertices U_i$ and V_i.
You are also given distinct vertices A,B,C on G.
Determine if there is a simple path connecting vertices A and C via vertex B.

What is a simple connected undirected graph?
A graph G is said to be a simple connected undirected graph when G is an undirected graph that is simple and connected.
A graph G is said to be an undirected graph when the edges of G have no direction.
A graph G is simple when G does not contain self-loops or multi-edges.
A graph G is connected when one can travel between all vertices of G via edges.

What is a simple path via vertex Z?
For vertices X and Y on a graph G, a simple path connecting X and Y is a sequence of distinct vertices $(v_1,v_2,\ldots,v_k)$ such that v_1=X, v_k=Y, and for every integer $i satisfying 1\leq i\leq k-1,$ there is an edge on G connecting vertices v_i and v_{i+1}.
$A simple path (v_1,v_2,\ldots,v_k)$ is said to be via vertex Z when there is an $i (2\leq i\leq k-1) satisfying v_i=Z$.

Input

The input is given from Standard Input in the following format:
N M
A B C
U_1 V_1
U_2 V_2
$\vdots$
U_M V_M

Output

If there is a simple path that satisfies the condition in the statement, print Yes; otherwise, print No.

Constraints

  • $3 \leq N \leq 2\times 10^5$
  • $N-1\leq M\leq\min\left(\frac{N(N-1)}{2},2\times 10^5\right)$
  • $1\leq A,B,C\leq N$
  • A, B, and C are all distinct.
  • $1\leq U_i<V_i\leq N$
  • The pairs (U_i,V_i) are all distinct.
  • All input values are integers.

Sample Input 1

6 7
1 3 2
1 2
1 5
2 3
2 5
2 6
3 4
4 5

Sample Output 1

Yes

One simple path connecting vertices 1 and 2 via vertex 3 is $1 \to$ $5 \to$ $4 \to$ $3 \to$ 2.
Thus, print Yes.

Sample Input 2

6 6
1 3 2
1 2
2 3
2 5
2 6
3 4
4 5

Sample Output 2

No

No simple path satisfies the condition. Thus, print No.

Sample Input 3

3 2
1 3 2
1 2
2 3

Sample Output 3

No

输入格式

见题面 Input 部分

输出格式

见题面 Output 部分

样例输入
6 7 1 3 2 1 2 1 5 2 3 2 5 2 6 3 4 4 5
样例输出
Yes