POJ1979 Red and Black

Description

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

#include <iostream> using namespace std; int n,m,ans; int sx,sy; int dx[4]={-1,0,1,0},dy[4]={0,-1,0,1}; bool visited[25][25]; char tile[25][25]; void dfs(int x,int y); int main() { while(cin>>m>>n&&n||m){ for(int i=0;i<n;i++){ for(int j=0;j<m;j++){ cin>>tile[i][j]; if(tile[i][j]=='@'){ sx=i;sy=j; } visited[i][j]=0; } } ans=1; dfs(sx,sy); cout<<ans<<endl; } return 0; } void dfs(int x,int y){ for(int i=0;i<4;i++){ int tx=x+dx[i],ty=y+dy[i]; if(tx>=0&&tx<n&&ty>=0&&ty<m&&tile[tx][ty]=='.'&&!visited[tx][ty]){ ++ans;visited[tx][ty]=1;dfs(tx,ty); } } }