9883: ABC306 —— G - Return to 1
[Creator : ]
Description
We have a directed graph with $N$ vertices and $M$ edges. The vertices are numbered from $1$ through $N$, and the $i$-th edge goes from vertex $U_i$ to vertex $V_i$.
You are currently at vertex $1$. Determine if you can make the following move $10^{10^{100}}$ times to end up at vertex $1$:
- choose an edge going from the vertex you are currently at, and move to the vertex that the edge points at.
Given $T$ test cases, solve each of them.
You are currently at vertex $1$. Determine if you can make the following move $10^{10^{100}}$ times to end up at vertex $1$:
- choose an edge going from the vertex you are currently at, and move to the vertex that the edge points at.
Given $T$ test cases, solve each of them.
Input
The input is given from Standard Input in the following format. Here, $\text{test}_i$ denotes the $i$-th test case.
```
$T$
$\text{test}_1$
$\text{test}_2$
$\vdots$
$\text{test}_T$
```
Each test case is given in the following format.
```
$N$ $M$
$U_1$ $V_1$
$U_2$ $V_2$
$\vdots$
$U_M$ $V_M$
```
```
$T$
$\text{test}_1$
$\text{test}_2$
$\vdots$
$\text{test}_T$
```
Each test case is given in the following format.
```
$N$ $M$
$U_1$ $V_1$
$U_2$ $V_2$
$\vdots$
$U_M$ $V_M$
```
Output
Print $T$ lines.
The $i$-th $(1\leq i \leq T)$ line should contain `Yes` if you can make the move described in the problem statement $10^{10^{100}}$ times to end up at vertex $1$, and `No` otherwise.
The $i$-th $(1\leq i \leq T)$ line should contain `Yes` if you can make the move described in the problem statement $10^{10^{100}}$ times to end up at vertex $1$, and `No` otherwise.
Constraints
- All input values are integers.
- $1\leq T \leq 2\times 10^5$
- $2\leq N \leq 2\times 10^5$
- $1\leq M \leq 2\times 10^5$
- The sum of $N$ over all test cases is at most $2 \times 10^5$.
- The sum of $M$ over all test cases is at most $2 \times 10^5$.
- $1 \leq U_i, V_i \leq N$
- $U_i \neq V_i$
- If $i\neq j$, then $(U_i,V_i) \neq (U_j,V_j)$.
- $1\leq T \leq 2\times 10^5$
- $2\leq N \leq 2\times 10^5$
- $1\leq M \leq 2\times 10^5$
- The sum of $N$ over all test cases is at most $2 \times 10^5$.
- The sum of $M$ over all test cases is at most $2 \times 10^5$.
- $1 \leq U_i, V_i \leq N$
- $U_i \neq V_i$
- If $i\neq j$, then $(U_i,V_i) \neq (U_j,V_j)$.
Sample 1 Input
4
2 2
1 2
2 1
3 3
1 2
2 3
3 1
7 10
1 6
6 3
1 4
5 1
7 1
4 5
2 1
4 7
2 7
4 3
7 11
1 6
6 3
1 4
5 1
7 1
4 5
2 1
4 7
2 7
4 3
3 7
Sample 1 Output
Yes
No
No
Yes
For the 1-st test case,
- You inevitably repeat visiting vertices 1→2→1→…. Thus, you will end up at vertex 1 after making the move $10^{{10}^{100}}$ times, so the answer is Yes.
For the 2-nd test case,
- You inevitably repeat visiting vertices 1→2→3→1→…. Thus, you will end up at vertex 2 after making the move $10^{{10}^{100}} times, so the answer is No.