HDU 3085 Nightmare Ⅱ

  • 2018-08-14
  • 25
  • 0

Description:

Last night, little erriyue had a horrible nightmare. He dreamed that he and his girl friend were trapped in a big maze separately. More terribly, there are two ghosts in the maze. They will kill the people. Now little erriyue wants to know if he could find his girl friend before the ghosts find them.
You may suppose that little erriyue and his girl friend can move in 4 directions. In each second, little erriyue can move 3 steps and his girl friend can move 1 step. The ghosts are evil, every second they will divide into several parts to occupy the grids within 2 steps to them until they occupy the whole maze. You can suppose that at every second the ghosts divide firstly then the little erriyue and his girl friend start to move, and if little erriyue or his girl friend arrive at a grid with a ghost, they will die.
Note: the new ghosts also can devide as the original ghost.

Input:

The input starts with an integer T, means the number of test cases.
Each test case starts with a line contains two integers n and m, means the size of the maze. (1<n, m<800)
The next n lines describe the maze. Each line contains m characters. The characters may be:
‘.’ denotes an empty place, all can walk on.
‘X’ denotes a wall, only people can’t walk on.
‘M’ denotes little erriyue
‘G’ denotes the girl friend.
‘Z’ denotes the ghosts.
It is guaranteed that will contain exactly one letter M, one letter G and two letters Z.

Output:

Output a single integer S in one line, denotes erriyue and his girlfriend will meet in the minimum time S if they can meet successfully, or output -1 denotes they failed to meet.

Sample Input:

3
5 6
XXXXXX
XZ..ZX
XXXXXX
M.G…
……
5 6
XXXXXX
XZZ..X
XXXXXX
M…..
..G…

10 10
……….
..X…….
..M.X…X.
X………
.X..X.X.X.
………X
..XX….X.
X….G…X
…ZX.X…
…Z..X..X

Sample Output:

1
1
-1

题目链接

有两个人分别在地图的不同位置,一个每个时间单位内可以走三步(或者说一步三格),另一个每个时间单位内可以走一步(或者说一步一格),地图上还有两个鬼魂,鬼魂每个时间单位内会向外扩散两格(可以穿墙),求两人相遇的最短时间。

双向bfs(宽度优先搜索),每次搜索更新一个时间单位,先判断与鬼魂的曼哈顿距离,之后记录两人分别可以到达的点位,若此点已被另一人标记则可以相遇,记录结果。

AC代码:

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