poj1979 DFS

Red and Black

Time Limit: 1000MS		Memory Limit: 30000K
Total Submissions: 18644		Accepted: 9907

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>
#include<cstdio>

using namespace std;
int dir[4][2]={0,1,0,-1,1,0,-1,0};
int w,h,cnt;
char map[25][25];

bool path(int x,int y)
{
    if(x<0||x>=h||y<0||y>=w)
        return false;
    return map[x][y]=='.';
}

void dfs(int x,int y)
{
    for(int i=0;i<4;i++)
    {
        int xx=x+dir[i][0];
        int yy=y+dir[i][1];
        if(path(xx,yy))
        {
            map[xx][yy]='#';
            cnt++;
            dfs(xx,yy);
        }
    }
}

int main()
{
    while(~scanf("%d%d",&w,&h),w+h)
    {
        for(int i=0;i<h;i++)
            scanf("%s",map[i]);
        cnt=1;
        for(int i=0;i<h;i++)
            for(int j=0;j<w;j++)
                if(map[i][j]=='@')
                {
                    dfs(i,j);
                    break;
                }
        printf("%d\n",cnt);
    }
    return 0;
}