hdu 1312 Red and Black(dfs入门)

#include <iostream>
#include <cstdio>
char map[21][21];
int H, W, starti, startj, num;                        //H行 W列
int dir[4][2] = {{-1,0}, {0,1}, {1,0}, {0,-1}};
void dfs(int x, int y)
{
    ++num;
    for (int i = 0; i < 4; ++i)
    {
        int fx = x + dir[i][0];
        int fy = y + dir[i][1];
        if (fx>=0 && fx<H && fy>=0 && fy<W && map[fx][fy] == '.')
        {
            map[fx][fy] = '#';
            dfs(fx, fy);
        }
    }
}
int main()
{
#ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
#endif
    while (scanf("%d %d", &W, &H) != EOF && W)
    {
        for (int i = 0; i < H; ++i)
            for (int j = 0; j < W; ++j)
            {
                std::cin >> map[i][j];
                if (map[i][j] == '@')
                {
                    starti = i;
                    startj = j;
                }
            }
        map[starti][startj] = '#';
        num = 0;
        dfs(starti, startj);
        printf("%d\n", num);
    }
    return 0;
}