ZOJ 2100 seed

挺简单的深搜题。。但是因为粗心，跑完一个test case后没有正确地更新field数组（开始时为求精简竟然在格子(i,j)为 false时不令field[i][j] = false，原因是我以为field[6][6]是全局变量，默认情况是初始化为false，所以想当然地以为如果格子(i,j)是false就不用多次一举。。可是我忘了每次运行一个test case后field会改的。。SB了

#include<iostream>
#include<fstream>
#include<cstring>
//#include "debug.h"
using namespace std;

bool field[6][6];   //有石头则为true,无石头则为false
bool seed[6][6];  //已经播种则为true,否则为false
int n,m;
//bool res;
int k = 0;  //已经播种的格子数
int total_seed = 0;  //可播种格子总数
bool res;

void dfs(int r,int c){
if(res) return;
if(k == total_seed){ res = true; return;}

if(seed[r][c] == true || field[r][c] == true) return;  //有石头或已播种
seed[r][c] = true;
++k;
if(k == total_seed){ res = true; return;}

if(r>0) dfs(r-1,c);
if(r<n-1) dfs(r+1,c);
if(c>0) dfs(r,c-1);
if(c<m-1) dfs(r,c+1);

--k;
seed[r][c] = false;
}

int main(){
//ifstream cin("input.txt");
while(cin>>n>>m){
if(n==0 && m==0) break;
char c;
for(int i=0;i<n;i++){
for(int j=0;j<m;j++){
cin>>c;
if(c=='S') field[i][j] = true;
else{ field[i][j] = false; ++total_seed;}
}
}
if(field[0][0] == true) cout<<"NO"<<endl;
dfs(0,0);
if(res) cout<<"YES"<<endl;
else cout<<"NO"<<endl;
memset(seed,0,36);
k = 0;
total_seed = 0;
res = false;
}
return 0;
}