HDU-Red and Black

Problem 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)

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

Source

Asia 2004, Ehime (Japan), Japan Domestic

代码：

#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;
int dir[4][2]={{1,0},{0,1},{-1,0},{0,-1}};
char map[33][33];
int vis[33][33];
int n,m;
int sum;
#define inf 0xfffffff
void dfs(int x,int y)
{
    int sx,sy,i;
    sum++;
    for(i=0;i<4;i++)
    {
        sx=x+dir[i][0];
        sy=y+dir[i][1];
        if(sx>=n ||sy>=m ||sx<0 ||sy<0 ||map[sx][sy]=='#' ||map[sx][sy]=='@')
            continue;
          map[sx][sy]='@';
              dfs(sx,sy);
    } 
}
int main()
{
    int i,j,x,y;
    while(scanf("%d%d",&m,&n)!=EOF&&n!=0 &&m!=0)
    {
        for(i=0;i<n;i++)
            scanf("%s",map[i]);
        for(i=0;i<n;i++)
            for(j=0;j<m;j++)
            {
                if(map[i][j]=='@')
                {
                    x=i;
                    y=j;         
                }
            }
            sum=0;
            dfs(x,y);
            printf("%d\n",sum);
    }
    return 0;
}

 然而这道题并不懂，什么广搜！