HDU 1241 Oil Deposits(dfs)

#include<cstdio>
#include<cmath>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
char mat[10][10];
int vis[10][10];
int ok,dx,dy;
int m,n,d;
int op[4][2]={0,1,1,0,0,-1,-1,0};
bool jiezhi(int x,int y,int rt)
{
  int now=abs(dx-x)+abs(dy-y);
  if(d-rt<now) return false;
  if((d-rt-now)%2!=0) return true;
  return true;
}
bool okn(int x,int y,int rt)
{
  if(x<0||x>=n||y<0||y>=m||rt>d||vis[x][y]==1||mat[x][y]=='X') return false;
  if(rt<d&&mat[x][y]=='D') return false;
  if(rt==d)
  {
    if(mat[x][y]=='D') ok=1;
    return false;
  }
  return true;
}
void dfs(int x,int y,int rt)
{
  if(jiezhi(x,y,rt)!=1||ok) return;
  int nx,ny;
  for(int i=0;i<4;i++)
  {
    nx=x+op[i][0];
    ny=y+op[i][1];
    if(okn(nx,ny,rt+1))
    {
      vis[nx][ny]=1;
      dfs(nx,ny,rt+1);
      vis[nx][ny]=0;
    }
  }
}
int main()
{
  int i,j,k;
  int sx,sy;
    while(scanf("%d%d%d",&n,&m,&d)!=EOF)
    {
        if(n==0||m==0||d==0) break;
        ok=0;
        for(i=0; i<n; i++)
        {
            scanf("%s",mat[i]);
        }
        memset(vis,0,sizeof(vis));

        for(i=0; i<n; i++)
            for(j=0; j<m; j++)
                {
                  if(mat[i][j]=='S')
                  {
                    sx=i;
                    sy=j;
                  }
                  else if(mat[i][j]=='D')
                  {
                    dx=i;dy=j;
                  }
                }
        if(jiezhi(sx,sy,0))
        {
          vis[sx][sy]=1;
          dfs(sx,sy,0);
        }
        if(ok) printf("YES\n");
        else printf("NO\n");
    }
  return 0;
}