HDU 1035 Robot Motion(dfs)

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int MAXN = 1005;
int MAP[MAXN][MAXN];
int vis[MAXN][MAXN];
int n,m,p,flag,ans,temp;
char ch;

void dfs(int x,int y,int step){
  if(flag)return ;
  int X,Y;
  if(MAP[x][y] == 1){
    X = x - 1;
    Y = y;
  }
  else if(MAP[x][y] == 2){
    X = x + 1;
    Y = y;
  }
  else if(MAP[x][y] == 3){
    X = x;
    Y = y - 1;
  }
  else {
    X = x;
    Y = y + 1;
  }
  if(X == 0 || Y == 0 || X == n+1 || Y == m+1){
    flag = 1;
    printf("%d step(s) to exit\n",vis[x][y]);
    return ;
  }
  if(vis[X][Y]){
    flag = 1;
    printf("%d step(s) before a loop of %d step(s)\n",vis[X][Y] - 1,step+ 1 - vis[X][Y]);
    ans = step + 1 - vis[X][Y];
    temp = vis[X][Y] - 1;
    return ;
  }
  vis[X][Y] = vis[x][y] + 1;
  dfs(X,Y,vis[X][Y]);
}

int main()
{
while(~scanf("%d%d",&n,&m)){
  flag = 0;
  if(n == 0 && m == 0) break;
  scanf("%d",&p);
  for(int i=1;i<=n;i++){
    for(int j=1;j<=m;j++){
      vis[i][j] = 0;
      cin>>ch;
      if(ch == 'N'){
        MAP[i][j] = 1;
      }
      else if(ch == 'S'){
        MAP[i][j] = 2;
      }
      else if(ch == 'W'){
        MAP[i][j] = 3;
      }
      else {
        MAP[i][j] = 4;
      }
    }
  }
  vis[1][p] = 1;
  dfs(1,p,0);
}
  return 0;
}