|Codeforces Round #648 (Div. 2)|
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:
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.
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.
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).
6 1 1 . 1 2 G. 2 2 #B G. 2 3 G.# B#. 3 3 #B. #.. GG. 2 2 #B B.
Yes Yes No No Yes Yes
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 $$$(2, 2)$$$.