Problem Statement
We define the density of a non-empty simple undirected graph as $\displaystyle\frac{(\text{number\ of\ edges})}{(\text{number\ of\ vertices})}$.
You are given positive integers $N$, $D$, and a simple undirected graph $G$ with $N$ vertices and $DN$ edges. The vertices of $G$ are numbered from $1$ to $N$, and the $i$-th edge connects vertex $A_i$ and vertex $B_i$. Determine whether $G$ satisfies the following condition.
Condition: Let $V$ be the vertex set of $G$. For any non-empty proper subset $X$ of $V$, the density of the induced subgraph of $G$ by $X$ is strictly less than $D$.
There are $T$ test cases to solve.
What is an induced subgraph? For a vertex subset $X$ of graph $G$, the induced subgraph of $G$ by $X$ is the graph with vertex set $X$ and edge set containing all edges of $G$ that connect two vertices in $X$. In the above condition, note that we only consider vertex subsets that are neither empty nor the entire set.
Constraints
$T \geq 1$$N \geq 1$$D \geq 1$- The sum of
$DN$over the test cases in each input file is at most$5 \times 10^4$. $1 \leq A_i < B_i \leq N \ \ (1 \leq i \leq DN)$$(A_i, B_i) \neq (A_j, B_j) \ \ (1 \leq i < j \leq DN)$
Input
The input is given from Standard Input in the following format:
T
\mathrm{case}_1
\mathrm{case}_2
\vdots
\mathrm{case}_T
Each test case $\mathrm{case}_i \ (1 \leq i \leq T)$ is in the following format:
N D
A_1 B_1
A_2 B_2
\vdots
A_{DN} B_{DN}
Output
Print $T$ lines. The $i$-th line should contain Yes if the given graph $G$ for the $i$-th test case satisfies the condition, and No otherwise.
样例
2
3 1
1 2
1 3
2 3
4 1
1 2
1 3
2 3
3 4
Yes
No
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