Red and Black（dfs水）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1312

Red and Black

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 15186    Accepted Submission(s): 9401

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

 

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<string>
using namespace std;
#define N 25
char mp[N][N];
int go[4][2] = {{1,0},{-1,0},{0,-1},{0,1}};

int n,m;
bool ck(int x, int y){
    if(x<n&&x>=0&&y<m&&y>=0) return true;
    else return false;
}
bool vis[N][N];
void dfs(int x, int y, int &sum)
{
    vis[x][y] = 1;
    bool fl = 0;
    for(int i = 0; i < 4; i++){
        int xx = x + go[i][0];
        int yy = y + go[i][1];
        if(ck(xx,yy)&&!vis[xx][yy]&&mp[xx][yy]=='.'){
            fl = 1;
            sum = sum+1;
            dfs(xx,yy,sum);
        }
    }
    if(fl==0) return;
}
int main()
{
    while(~scanf("%d%d",&m,&n))
    {
        int x, y;
        if(n==0&&m==0) break;
        getchar();
        for(int i = 0; i < n; i++){
            for(int j = 0; j < m; j++){
                scanf("%c",&mp[i][j]);
                if(mp[i][j]=='@'){ x = i; y = j; }
            }
            getchar();
        }
        memset(vis,0,sizeof(vis));
        int sum = 0;
        dfs(x,y,sum);
        printf("%d\n",sum+1);
    }
    return 0;
}