HDOj 1010 DFS优化

 #include<cstdio>
 #include<cstring>
 int sx[]={,,,-};
 int sy[]={,,-,};
 int g[][];
 int x1,y1,x2,y2;
 int step;
 int n,m,t;
 void dfs(int x,int y,int c_step)
 {

     if(x==x2&&y==y2&&c_step==t)
     {

         step=;return;
     }
     if((x>x2?x-x2:x2-x)+(y>y2?y-y2:y2-y)+c_step>t)//小剪
     {
         return;
     }
     int i;
     for(i=;i<;i++)
     {
         int xx,yy;
         xx=x+sx[i];
         yy=y+sy[i];
         if(xx>=&&xx<=n&&yy>=&&yy<=m&&g[xx][yy]==&&c_step+<=t)
         {
             g[xx][yy]=;
             dfs(xx,yy,c_step+);
             if(step==)//强力缩短时间
                 return;
             g[xx][yy]=;
         }
     }

 }
 int main()
 {
     int i,j,sum;
     char c;
     while(scanf("%d %d %d",&n,&m,&t)!=EOF)
     {
         if(!n&&!m&&!t)break;
         step=;
         sum=;
         getchar();
         for(i=;i<=n;i++)
         {
             for(j=;j<=m;j++)
             {
                 c=getchar();
                 if(c=='S')
                     x1=i,y1=j;
                 else if(c=='D')
                     x2=i,y2=j,g[i][j]=;
                 else if(c=='X')
                     g[i][j]=;
                 else if(c=='.')
                     g[i][j]=,sum++;
             }
             getchar();
         }
         if(sum+<t||(t+x1+y1+x2+y2)%==)//奇偶性判别与可达性判别
             printf("NO\n");
         else
         {
             g[x1][y1]=;
             dfs(x1,y1,);
             if(step)
                 printf("YES\n");
             else
                 printf("NO\n");
         }
     }
     return ;
 }