FZU 2150 Fire Game
Problem Description
Fat brother and Maze are playing a kind of special (hentai) game on an board (N rows, M columns). At the beginning, each grid of this board is consisting of grass or just empty and then they start to fire all the grass. Firstly they choose two grids which are consisting of grass and set fire. As we all know, the fire can spread among the grass. If the grid is firing at time , the grid which is adjacent to this grid will fire at time which refers to the grid . This process ends when no new grid get fire. If then all the grid which are consisting of grass is get fired, Fat brother and Maze will stand in the middle of the grid and playing a MORE special (hentai) game. (Maybe it’s the OOXX game which decrypted in the last problem, who knows.)
You can assume that the grass in the board would never burn out and the empty grid would never get fire.
Note that the two grids they choose can be the same.
Input
The first line of the date is an integer T, which is the number of the text cases.
Then T cases follow, each case contains two integers and indicate the size of the board. Then goes N line, each line with M character shows the board. ‘#’ Indicates the grass. You can assume that there is at least one grid which is consisting of grass in the board.
Output
For each case, output the case number first, if they can play the MORE special (hentai) game (fire all the grass), output the minimal time they need to wait after they set fire, otherwise just output -1. See the sample input and output for more details.
Sample Input
4
3 3
.#.
###
.#.
3 3
.#.
#.#
.#.
3 3
...
#.#
...
3 3
###
…#
#.#
Sample Output
Case 1: 1
Case 2: -1
Case 3: 0
Case 4: 2
Translation
给一张平面地图,'#‘表示草地,’.'表示空地。两个人 和,觉得找分别找一块草地放把火,火会向上下左右的草地蔓延,每前进一格需要一分钟,问至少需要几分钟把草地烧光。
两人可能会选择同一块草地,火是烧不到空地上的。
Idea
暴力枚举地图上的两块草地组合,两块草地同时入队进行,完成后检查是否所有的草地都被访问过,如果没有就继续枚举,否则更新答案。
Code
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