[POJ]poj1573(模拟)

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
#define rep(i,n) for(int i=1;i<=n;i++)
#define pb push_back
#define mp make_pair
#define LL long long
#define nd second
#define st first

#define pii pair<int , int> 

const int N = 2e1+7;

const int dx[]={1,-1,0,0};
const int dy[]={0,0,1,-1};

int n,m,s,cnt;

int a[N][N],vis[N][N],tag[N][N];

void dfs(int x,int y,int step){
    if(x>n||y>m||x<1||y<1){
        printf("%d step(s) to exit\n",step);
        return;
    }
    if(tag[x][y]==-1)tag[x][y]=step;
    vis[x][y]++;
    
    if(vis[x][y]==2){
        printf("%d step(s) before a loop of %d step(s)\n",tag[x][y],step-tag[x][y]);
        return ;
    }
    int nx=x+dx[a[x][y]];
    int ny=y+dy[a[x][y]];
    dfs(nx,ny,step+1);
}

void init(){
    memset(vis,0,sizeof(vis));
    memset(tag,-1,sizeof(tag));
}

int main(){
    while(cin>>n>>m>>s){ 
        if(!n)return 0; 
        
        init();
        
        rep(i,n){
            string s;
            cin>>s;
            for(int j=0;j<s.size();j++){
                if(s[j]==‘S‘)a[i][j+1]=0;
                if(s[j]==‘N‘)a[i][j+1]=1;
                if(s[j]==‘E‘)a[i][j+1]=2;
                if(s[j]==‘W‘)a[i][j+1]=3;
                }    
            }
        dfs(1,s,0);
    } 
}