poj 1573 Robot Motion

题目：http://poj.org/problem?id=1573

题意：已知坐标系大小，和初始的最上面的位置，根据命令求是否能出去，或者一直循环

这就是我建的系，画的有点难看哈！

#include <iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
using namespace std;
char map[500][500];
int vis[500][500];

int dx[5]={0,0,-1,1};//分别代表N,S,W,E
int dy[5]={1,-1,0,0};
int main()
{
    int i,j,a,b,t,f,sum,x;
    while(cin>>a>>b>>t&&(a!=0||b!=0||t!=0))
    {
        sum=0;
        memset(vis,0,sizeof(vis));
        for(j=a; j>=1; j--)
        {
            for(i=1; i<=b; i++)
            cin>>map[i][j];
        }
        i = t; j = a;
        while(1)
        {
            sum++;
            vis[i][j]=sum;
            if(map[i][j]=='N') {i+=dx[0]; j+=dy[0];}
            else if(map[i][j]=='S') {i+=dx[1]; j+=dy[1];}
            else if(map[i][j]=='W') {i+=dx[2]; j+=dy[2];}
            else if(map[i][j]=='E') {i+=dx[3]; j+=dy[3];}
             if(vis[i][j])
            {
                f=1;
                x=vis[i][j];
                break;
            }
            if(i>b||j>a || i<=0 ||j<=0)
            {
                f=2;
                break;
            }
        }
       if(f==2)
       {
           printf("%d step(s) to exit
",sum);
       }
       else
       {
           printf("%d step",x-1);
           printf("(s)");
           printf(" before a loop of %d step",sum-x+1);
           printf("(s)");
           printf("
");
       }
    }
    return 0;
}