A14995 | Cross Xor

There is a grid with $r$ rows and $c$ columns, where the square on the $i$ -th row and $j$ -th column has an integer $a_{i, j}$ written on it. Initially, all elements are set to $0$ . We are allowed to do the following operation:

- Choose indices $1 \le i \le r$ and $1 \le j \le c$ , then replace all values on the same row or column as $(i, j)$ with the value xor $1$ . In other words, for all $a_{x, y}$ where $x=i$ or $y=j$ or both, replace $a_{x, y}$ with $a_{x, y}$ xor $1$ .

You want to form grid $b$ by doing the above operations a finite number of times. However, some elements of $b$ are missing and are replaced with '?' instead.

Let $k$ be the number of '?' characters. Among all the $2^k$ ways of filling up the grid $b$ by replacing each '?' with '0' or '1', count the number of grids, that can be formed by doing the above operation a finite number of times, starting from the grid filled with $0$ . As this number can be large, output it modulo $998244353$ .

The first line contains two integers $r$ and $c$ ( $1 \le r, c \le 2000$ ) — the number of rows and columns of the grid respectively.

The $i$ -th of the next $r$ lines contain $c$ characters $b_{i, 1}, b_{i, 2}, \ldots, b_{i, c}$ ( $b_{i, j} \in \{0, 1, ?\}$ ).

Print a single integer representing the number of ways to fill up grid $b$ modulo $998244353$ .