hud 1312

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. 

InputThe 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) 
OutputFor 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

解题思路：
直接dfs,
实现代码：

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <bitset>
using namespace std;

#define rep(i,a,b) for (int i=(a),_ed=(b);i<=_ed;i++)
#define per(i,a,b) for (int i=(b),_ed=(a);i>=_ed;i--)
#define pb push_back

const int inf_int = 2e9;
const long long inf_ll = 2e18;
#define inf_add 0x3f3f3f3f
#define mod 1000000007
#define LL long long
#define ULL unsigned long long
#define MS0(X) memset((X), 0, sizeof((X)))
#define SelfType int
SelfType Gcd(SelfType p,SelfType q){return q==0?p:Gcd(q,p%q);}
SelfType Pow(SelfType p,SelfType q){SelfType ans=1;while(q){if(q&1)ans=ans*p;p=p*p;q>>=1;}return ans;}
#define Sd(X) int (X); scanf("%d", &X)
#define Sdd(X, Y) int X, Y; scanf("%d%d", &X, &Y)
#define Sddd(X, Y, Z) int X, Y, Z; scanf("%d%d%d", &X, &Y, &Z)
#define reunique(v) v.resize(std::unique(v.begin(), v.end()) - v.begin())
#define all(a) a.begin(), a.end()
#define   mem(x,v)      memset(x,v,sizeof(x))
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
typedef vector<int> vi;
typedef vector<long long> vll;
#define PI acos(-1.0)
#define exp 1e-9
char mp[25][25];
int vis[25][25];
int ans;
void dfs(int x,int y)
{
    if(mp[x-1][y]=='.'&&vis[x-1][y]==0){
        ans++;
        vis[x-1][y] = 1;
        dfs(x-1,y);
    }
    if(mp[x][y-1]=='.'&&vis[x][y-1]==0){
        ans++;
        vis[x][y-1] = 1;
        dfs(x,y-1);
    }
    if(mp[x][y+1]=='.'&&vis[x][y+1]==0){
        ans++;
        vis[x][y+1]= 1;
        dfs(x,y+1);
    }
    if(mp[x+1][y]=='.'&&vis[x+1][y]==0){
        ans++;
        vis[x+1][y] = 1;
        dfs(x+1,y);
    }
}
int main()
{
    int n,m,i,j;
    while(scanf("%d%d",&m,&n),m+n)
    {
        getchar();
        ans=0;
        memset(vis,0,sizeof(vis));
        memset(mp,'#',sizeof(mp));
        for(i=1;i<=n;i++)
        {
            for(j=1;j<=m;j++)
            {
                scanf("%c",&mp[i][j]);
            }
            getchar();
        }
        for(i=1;i<=n;i++)
        {
            for(j=1;j<=m;j++)
            {
                if(mp[i][j]=='@')
                {
                    ans++;
                    vis[i][j]=1;
                    dfs(i,j);
                    i=n;
                    j=m;
                }
            }
        }
        printf("%d
",ans);
    }
    return 0;
}