POJ 1979 Red and Black

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstdlib>
#include <cstring>
#include <queue>
using namespace std;

//与POJ_2386水洼题相似
//dfs深度优先搜索

int ans,dis[21][21],w,h;
char room[21][21];
int dx[4]={1,0,0,-1};
int dy[4]={0,1,-1,0};

void dfs(int x,int y)
{
int i;
for(i=0;i<4;i++){
int x0=x+dx[i],y0=y+dy[i];
if(room[x0][y0]=='.' && dis[x0][y0]==0 && x0>=0 && y0>=0 && x0<h && y0<w){
dis[x0][y0]=1;
ans++;
dfs(x0,y0);
}
}
return;
}

int main()
{
int i,j,x0,y0;
cin>>w>>h;
getchar();
while(w||h){
ans=0;
memset(dis,0,sizeof(dis));
for(i=0;i<h;i++)  gets(room[i]);
for(i=0;i<h;i++){
for(j=0;j<w;j++){
if(room[i][j]=='@'){
dis[i][j]=1;
ans++;
dfs(i,j);
}
}
}
printf("%d\n",ans);
cin>>w>>h;
getchar();
}
return 0;
}