题库练习 Infinite Maze
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A8645 | Infinite Maze

时间限制1s
内存限制256MB
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题目描述

We've got a rectangular $n×m$ -cell maze. Each cell is either passable, or is a wall (impassable). A little boy found the maze and cyclically tiled a plane with it so that the plane became an infinite maze. Now on this plane cell $(x,y)$ is a wall if and only if cell ![](/uploads/acgo/image/a955819aabf0ce59_f5d72f1ef4fa.jpeg) is a wall.

In this problem ![](/uploads/acgo/image/e09071e31f9d933a_e82dbe5cc621.jpeg) is a remainder of dividing number $a$ by number $b$ .

The little boy stood at some cell on the plane and he wondered whether he can walk infinitely far away from his starting position. From cell $(x,y)$ he can go to one of the following cells: $(x,y-1)$ , $(x,y+1)$ , $(x-1,y)$ and $(x+1,y)$ , provided that the cell he goes to is not a wall.

输入格式

The first line contains two space-separated integers $n$ and $m$ ( $1<=n,m<=1500$ ) — the height and the width of the maze that the boy used to cyclically tile the plane.

Each of the next $n$ lines contains $m$ characters — the description of the labyrinth. Each character is either a "\#", that marks a wall, a ".", that marks a passable cell, or an "S", that marks the little boy's starting point.

The starting point is a passable cell. It is guaranteed that character "S" occurs exactly once in the input.

输出格式

Print "Yes" (without the quotes), if the little boy can walk infinitely far from the starting point. Otherwise, print "No" (without the quotes).

输入输出样例

输入 #1
5 4
##.#
##S#
#..#
#.##
#..#
输出 #1
Yes
输入 #2
5 4
##.#
##S#
#..#
..#.
#.##
输出 #2
No
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