CF1365D.Solve The Maze

Vivek has encountered a problem. He has a maze that can be represented as an $n \times m$ grid. Each of the grid cells may represent the following:

• Empty — '.'
• Wall — '#'
• Good person — 'G'
• Bad person — 'B'

The only escape from the maze is at cell $(n, m)$.

A person can move to a cell only if it shares a side with their current cell and does not contain a wall. Vivek wants to block some of the empty cells by replacing them with walls in such a way, that all the good people are able to escape, while none of the bad people are able to. A cell that initially contains 'G' or 'B' cannot be blocked and can be travelled through.

Help him determine if there exists a way to replace some (zero or more) empty cells with walls to satisfy the above conditions.

It is guaranteed that the cell $(n,m)$ is empty. Vivek can also block this cell.

维韦克遇到了一个问题。他有一个迷宫，可以表示为一个 $n \times m$ 的网格。网格中的每个单元格可能表示以下几种类型之一：

• 空单元格 — '.'
• 墙 — '#'
• 好人 — 'G'
• 坏人 — 'B'

迷宫中唯一的出口位于单元格 $(n, m)$。

一个人只能移动到与其当前单元格共享一条边（即上下左右相邻）且不为墙的单元格。维韦克希望将一些空单元格（即 '.'）替换为墙（即 '#'），使得所有好人都能成功逃出迷宫，而所有坏人都无法逃出。初始时包含 'G' 或 'B' 的单元格不能被封锁，且可以被通行（即好人和坏人均可经过彼此所在位置，也可经过对方所在位置）。

请帮助他判断：是否存在一种方式（可替换零个或多个空单元格为墙），满足上述条件。

题目保证单元格 $(n,m)$ 初始为空（即 '.'）。维韦克也可以将该出口单元格封锁（即改为 '#'）。

The first line contains one integer $t$ $(1 \le t \le 100)$ — the number of test cases. The description of the test cases follows.

The first line of each test case contains two integers $n$, $m$ $(1 \le n, m \le 50)$ — the number of rows and columns in the maze.

Each of the next $n$ lines contain $m$ characters. They describe the layout of the maze. If a character on a line equals '.', the corresponding cell is empty. If it equals '#', the cell has a wall. 'G' corresponds to a good person and 'B' corresponds to a bad person.

第一行包含一个整数 $t$（$1 \le t \le 100$）——测试用例的数量。随后是各测试用例的描述。

每个测试用例的第一行包含两个整数 $n$、$m$（$1 \le n, m \le 50$）——分别表示迷宫的行数和列数。

接下来的 $n$ 行，每行包含 $m$ 个字符，用于描述迷宫的布局：若某行为 '.'，则对应格子为空；若为 '#'，则对应格子为墙；'G' 表示一个好人，'B' 表示一个坏人。

For each test case, print "Yes" if there exists a way to replace some empty cells with walls to satisfy the given conditions. Otherwise print "No"

You may print every letter in any case (upper or lower).

对于每个测试用例，如果存在一种方式将某些空单元格替换为墙壁以满足给定条件，则输出“Yes”；否则输出“No”。

你可以以任意大小写（大写或小写）输出每个字母。

For the first and second test cases, all conditions are already satisfied.

For the third test case, there is only one empty cell $(2,2)$, and if it is replaced with a wall then the good person at $(1,2)$ will not be able to escape.

For the fourth test case, the good person at $(1,1)$ cannot escape.

For the fifth test case, Vivek can block the cells $(2,3)$ and $(2,2)$.

For the last test case, Vivek can block the destination cell $(2, 2)$.

对于第一和第二个测试用例，所有条件均已满足。

对于第三个测试用例，仅有一个空单元格 $(2,2)$；若将其替换为墙，则位于 $(1,2)$ 的好人将无法逃脱。

对于第四个测试用例，位于 $(1,1)$ 的好人无法逃脱。

对于第五个测试用例，Vivek 可以封锁单元格 $(2,3)$ 和 $(2,2)$。

对于最后一个测试用例，Vivek 可以封锁目标单元格 $(2, 2)$。