There is a rectangular room, covered with square tiles. Each tile is colored either red or black. A man is standing on a black tile. From a tile, he can move to one of four adjacent tiles. But he can't move on red tiles, he can move only on black tiles.
Write a program to count the number of black tiles which he can reach by repeating the moves described above.
Input
The input consists of multiple data sets. A data set starts with a line containing two positive integers W and H; W and H are the numbers of tiles in the x- and y- directions, respectively. W and H are not more than 20.
There are H more lines in the data set, each of which includes W characters. Each character represents the color of a tile as follows.
'.' - a black tile
'#' - a red tile
'@' - a man on a black tile(appears exactly once in a data set)
The end of the input is indicated by a line consisting of two zeros.
Output
For each data set, your program should output a line which contains the number of tiles he can reach from the initial tile (including itself).
Sample Input
6 9
....#.
.....#
......
......
......
......
......
#@...#
.#..#.
11 9
.#.........
.#.#######.
.#.#.....#.
.#.#.###.#.
.#.#..@#.#.
.#.#####.#.
.#.......#.
.#########.
...........
11 6
..#..#..#..
..#..#..#..
..#..#..###
..#..#..#@.
..#..#..#..
..#..#..#..
7 7
..#.#..
..#.#..
###.###
...@...
###.###
..#.#..
..#.#..
0 0
Sample Output
45
59
6
13
题意：给出n*m矩阵，有红格与黑格，不能走红格，只能走黑格，
要求输出从一个起始点出发能够踩到的黑色格子数
题解：
从起点开始深度搜索，搜过的标记不再访问，记录搜过的数量，输出遍历的次数
#include<iostream>
#include<algorithm>
using namespace std;
int w;
int h;
char path[35][35];
int dfs(int x,int y){
if(path[x][y]=='#'||x<0||y<0||x>=w||y>=h)
return 0;
else{
path[x][y]='#';
//这条路可以走，先+1，再打算往四个方向走
return 1+dfs(x-1,y)+dfs(x+1,y)+dfs(x,y-1)+dfs(x,y+1);
}
}
int main(){
int x;
int y;
while((cin>>h>>w),(w||h)){
for(int i=0;i<w;i++)
for(int j=0;j<h;j++){
cin>>path[i][j];
if(path[i][j]=='@'){
x=i;
y=j;
}
}
cout<<dfs(x,y)<<endl;
}
return 0;
}
