Score : $200$ points

问题描述

有 $N$ 名编号为 $1,2,\ldots,N$ 的人。

共举行了 $M$ 场聚会。在第 $i$ 场 $(1\leq i \leq M)$ 聚会中，有 $k_i$ 人参加，他们是编号为 $x_{i,1},x_{i,2},\ldots,x_{i,k_i}$ 的人。

确定是否每两个人至少都曾参加过同一场聚会。

以上为通义千问 qwen-max 翻译，仅供参考。

Problem Statement

There are $N$ people numbered $1,2,\ldots,N$.

$M$ parties were held. $k_i$ people attended the $i$-th $(1\leq i \leq M)$ party, and they were People $x_{i,1},x_{i,2},\ldots,x_{i,k_i}$.

Determine if every two people attended the same party at least once.

Constraints

• $2\leq N \leq 100$
• $1\leq M \leq 100$
• $2\leq k_i \leq N$
• $1\leq x_{i,1}<x_{i,2}<\ldots < x_{i,k_i}\leq N$
• All values in the input are integers.

Input

The input is given from Standard Input in the following format:

$N$ $M$

$k_1$ $x_{1,1}$ $x_{1,2}$ $\ldots$ $x_{1,k_1}$

$\vdots$

$k_M$ $x_{M,1}$ $x_{M,2}$ $\ldots$ $x_{M,k_M}$

Output

Print Yes if every two people attended the same party at least once; print No otherwise.

Sample Input 1

3 3
2 1 2
2 2 3
2 1 3

Sample Output 1

Yes

Both Person $1$ and Person $2$ attended the $1$-st party.

Both Person $2$ and Person $3$ attended the $2$-nd party.

Both Person $1$ and Person $3$ attended the $3$-rd party.

Therefore, every two people attended the same party at least once, so the answer is Yes.

Sample Input 2

4 2
3 1 2 4
3 2 3 4

Sample Output 2

No

Person $1$ and Person $3$ did not attend the same party, so the answer is No.

update @ 2024/3/10 11:27:29