Red and Black

        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

4559613

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;}