Euclid's nightmare

题意翻译

给定包含 $n$ 个 $m$ 维向量的向量集 $S$，每个向量 $\overrightarrow{a}$ 满足 $a_i\in \{0,1\}$ 且 $\sum\limits_{i=1}^ma_i\in\{1,2\}$。定义向量加法 $\overrightarrow{c}=\overrightarrow{a}+\overrightarrow{b}$ 为 $\forall i\in \Z\cap[1,m], c_i=a_i\oplus b_i$，其中 $\oplus$ 表示异或运算。 求极大线性空间 $T$ 使得 $T$ 的一组基 $A$ 均为 $S$ 中元素。输出 $|T|,|A|$ 以及 $A$。 要求在 $|A|$ 最小前提下 $A$ 关于向量编号字典序最小。 ### 输入格式 第一行 $n,m$ 以下 $n$ 行，每行先输入 $\sum\limits_{i=1}^ma_i$，接下来输入 $\sum\limits_{i=1}^ma_i$ 个数字 $k$ 表示 $a_k=1$。 ### 输出格式 第一行输出 $|T|$ 和 $|A|$ 第二行输出 $A$ 的每个向量，按编号排序并只需输出编号。

题目描述

You may know that Euclid was a mathematician. Well, as it turns out, Morpheus knew it too. So when he wanted to play a mean trick on Euclid, he sent him an appropriate nightmare. In his bad dream Euclid has a set $ S $ of $ n $ $ m $ -dimensional vectors over the $ \mathbb{Z}_2 $ field and can perform vector addition on them. In other words he has vectors with $ m $ coordinates, each one equal either $ 0 $ or $ 1 $ . Vector addition is defined as follows: let $ u+v = w $ , then $ w_i = (u_i + v_i) \bmod 2 $ . Euclid can sum any subset of $ S $ and archive another $ m $ -dimensional vector over $ \mathbb{Z}_2 $ . In particular, he can sum together an empty subset; in such a case, the resulting vector has all coordinates equal $ 0 $ . Let $ T $ be the set of all the vectors that can be written as a sum of some vectors from $ S $ . Now Euclid wonders the size of $ T $ and whether he can use only a subset $ S' $ of $ S $ to obtain all the vectors from $ T $ . As it is usually the case in such scenarios, he will not wake up until he figures this out. So far, things are looking rather grim for the philosopher. But there is hope, as he noticed that all vectors in $ S $ have at most $ 2 $ coordinates equal $ 1 $ . Help Euclid and calculate $ |T| $ , the number of $ m $ -dimensional vectors over $ \mathbb{Z}_2 $ that can be written as a sum of some vectors from $ S $ . As it can be quite large, calculate it modulo $ 10^9+7 $ . You should also find $ S' $ , the smallest such subset of $ S $ , that all vectors in $ T $ can be written as a sum of vectors from $ S' $ . In case there are multiple such sets with a minimal number of elements, output the lexicographically smallest one with respect to the order in which their elements are given in the input. Consider sets $ A $ and $ B $ such that $ |A| = |B| $ . Let $ a_1, a_2, \dots a_{|A|} $ and $ b_1, b_2, \dots b_{|B|} $ be increasing arrays of indices elements of $ A $ and $ B $ correspondingly. $ A $ is lexicographically smaller than $ B $ iff there exists such $ i $ that $ a_j = b_j $ for all $ j < i $ and $ a_i < b_i $ .

输入输出格式

输入格式

In the first line of input, there are two integers $ n $ , $ m $ ( $ 1 \leq n, m \leq 5 \cdot 10^5 $ ) denoting the number of vectors in $ S $ and the number of dimensions. Next $ n $ lines contain the description of the vectors in $ S $ . In each of them there is an integer $ k $ ( $ 1 \leq k \leq 2 $ ) and then follow $ k $ distinct integers $ x_1, \dots x_k $ ( $ 1 \leq x_i \leq m $ ). This encodes an $ m $ -dimensional vector having $ 1 $ s on coordinates $ x_1, \dots x_k $ and $ 0 $ s on the rest of them. Among the $ n $ vectors, no two are the same.

输出格式

In the first line, output two integers: remainder modulo $ 10^9+7 $ of $ |T| $ and $ |S'| $ . In the second line, output $ |S'| $ numbers, indices of the elements of $ S' $ in ascending order. The elements of $ S $ are numbered from $ 1 $ in the order they are given in the input.

输入输出样例

输入样例 #1

3 2
1 1
1 2
2 2 1

输出样例 #1

4 2
1 2

输入样例 #2

2 3
2 1 3
2 1 2

输出样例 #2

4 2
1 2

输入样例 #3

3 5
2 1 2
1 3
1 4

输出样例 #3

8 3
1 2 3

说明

In the first example we are given three vectors: - $ 10 $ - $ 01 $ - $ 11 $ It turns out that we can represent all vectors from our $ 2 $ -dimensional space using these vectors: - $ 00 $ is a sum of the empty subset of above vectors; - $ 01 = 11 + 10 $ , is a sum of the first and third vector; - $ 10 = 10 $ , is just the first vector; - $ 11 = 10 + 01 $ , is a sum of the first and the second vector. Hence, $ T = \{00, 01, 10, 11\} $ . We can choose any two of the three vectors from $ S $ and still be able to obtain all the vectors in $ T $ . In such a case, we choose the two vectors which appear first in the input. Since we cannot obtain all vectors in $ T $ using only a single vector from $ S $ , $ |S'| = 2 $ and $ S' = \{10, 01\} $ (indices $ 1 $ and $ 2 $ ), as set $ \{1, 2 \} $ is lexicographically the smallest. We can represent all vectors from $ T $ , using only vectors from $ S' $ , as shown below: - $ 00 $ is a sum of the empty subset; - $ 01 = 01 $ is just the second vector; - $ 10 = 10 $ is just the first vector; - $ 11 = 10 + 01 $ is a sum of the first and the second vector.

题意翻译

给定包含 $n$ 个 $m$ 维向量的向量集 $S$，每个向量 $\overrightarrow{a}$ 满足 $a_i\in \{0,1\}$ 且 $\sum\limits_{i=1}^ma_i\in\{1,2\}$。定义向量加法 $\overrightarrow{c}=\overrightarrow{a}+\overrightarrow{b}$ 为 $\forall i\in \Z\cap[1,m], c_i=a_i\oplus b_i$，其中 $\oplus$ 表示异或运算。 求极大线性空间 $T$ 使得 $T$ 的一组基 $A$ 均为 $S$ 中元素。输出 $|T|,|A|$ 以及 $A$。 要求在 $|A|$ 最小前提下 $A$ 关于向量编号字典序最小。 ### 输入格式 第一行 $n,m$ 以下 $n$ 行，每行先输入 $\sum\limits_{i=1}^ma_i$，接下来输入 $\sum\limits_{i=1}^ma_i$ 个数字 $k$ 表示 $a_k=1$。 ### 输出格式 第一行输出 $|T|$ 和 $|A|$ 第二行输出 $A$ 的每个向量，按编号排序并只需输出编号。