CSES - Monsters
Xem dạng PDFYou and some monsters are in a labyrinth. When taking a step to some direction in the labyrinth, each monster may simultaneously take one as well. Your goal is to reach one of the boundary squares without ever sharing a square with a monster.
Your task is to find out if your goal is possible, and if it is, print a path that you can follow. Your plan has to work in any situation; even if the monsters know your path beforehand.
Input
- The first input line has two integers ~n~ and ~m~: the height and width of the map.
After this there are ~n~ lines of ~m~ characters describing the map. Each character is . (floor), # (wall), A (start), or M (monster). There is exactly one A in the input.
Output
- First print "YES" if your goal is possible, and "NO" otherwise.
If your goal is possible, also print an example of a valid path (the length of the path and its description using characters D, U, L, and R). You can print any path, as long as its length is at most ~n \cdot m~ steps.
Constraints
- ~1 \le n,m \le 1000~
Example Input
5 8
########
#M..A..#
#.#.M#.#
#M#..#..
#.######
Example Output
YES
5
RRDDR
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