A886.Cow Navigation--Gold
提高+/省选-
通过率:0%
时间限制:1.00s
内存限制:128MB
题目描述
Bessie has gotten herself stuck on the wrong side of Farmer John's barn again,
and since her vision is so poor, she needs your help navigating across the
barn.
The barn is described by an N×N grid of square cells (2≤N≤20), some being empty and some containing impassable haybales. Bessie starts
in the lower-left corner (cell 1,1) and wants to move to the upper-right
corner (cell N,N). You can guide her by telling her a sequence of
instructions, each of which is either "forward", "turn left 90 degrees", or
"turn right 90 degrees". You want to issue the shortest sequence of
instructions that will guide her to her destination. If you instruct Bessie to
move off the grid (i.e., into the barn wall) or into a haybale, she will not
move and will skip to the next command in your sequence.
Unfortunately, Bessie doesn't know if she starts out facing up (towards cell
1,2) or right (towards cell 2,1). You need to give the shortest sequence of
directions that will guide her to the goal regardless of which case is true.
Once she reaches the goal she will ignore further commands.
输入格式
The first line of input contains N.
Each of the N following lines contains a string of exactly N characters,
representing the barn. The first character of the last line is cell 1,1. The
last character of the first line is cell N, N.
Each character will either be an H to represent a haybale or an E to represent
an empty square.
It is guaranteed that cells 1,1 and N,N will be empty, and furthermore it is
guaranteed that there is a path of empty squares from cell 1,1 to cell N,N.
输出格式
On a single line of output, output the length of the shortest sequence of
directions that will guide Bessie to the goal, irrespective whether she starts
facing up or right.
输入输出样例
输入#1
3 EHE EEE EEE
输出#1
9
说明/提示
In this example, the instructions "Forward, Right, Forward, Forward, Left,
Forward, Left, Forward, Forward" will guide Bessie to the destination
irrespective of her starting orientation.