Labyrinth
You are given a map of a labyrinth, and your task is to determine a path from start to end. You can walk left, right, up and down.
Input
The first input line has two integers \(n\) and \(m\): the height and width of the map. Then there are n lines of m characters describing the labyrinth. Each character is . (floor), # (wall), \(A\) (start), or \(B\) (end). There is exactly one \(A\) and one \(B\) in the input.
Output
Print "YES", if there is a path, and "NO" otherwise.
Constraints
\(1 \le n,m \le 1000\)
Sample Input:
5 8
########
#.A#...#
#.##.#B#
#......#
########
Sample Output:
YES
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