HDU 2612 Find a way

这是一个双向搜索题，我用BFS把所有的点都搜索到；再进行两次搜索的比较；

#include<cstdio>
#include<cstring>
#include<iostream>
using namespace std;
class Node
{
public:
     int x , y ;
     int step;
     int num;    
};
Node queue[80024];
int step[2][204][204],N,M;
int d[4][2] = { 0,1,1,0,-1,0,0,-1 };
char map[204][204];
int BFS( int x1,int y1, int x2 ,int y2 )
{
   int min = 0X7fffffff;
   int first = 0 , end = 0;
   Node t ;
   t.x = x1; t.y = y1;
   t.step = 0 , t.num = 0;
   queue[end] = t;
   end++;
   t.x = x2; t.y = y2;
   t.step = 0 , t.num = 1;
   queue[end]  =t;
   end++;
   step[0][x1][y1] = 0;
   step[1][x2][y2] = 0;
   while( first < end )
   {
       t = queue[ first ];
       for( int i = 0; i < 4 ; i++ )
       {
         int dx = d[i][0] + t.x;
         int dy = d[i][1] + t.y;
         if( step[t.num][dx][dy]==-1 )
         {
             if( map[dx][dy] !='#'&&map[dx][dy] != 0)
             {
                 step[t.num][dx][dy] = t.step + 1;
                 queue[end].x = dx;
                 queue[end].y = dy;
                 queue[end].num = t.num;
                 queue[end].step = t.step + 1;
                 end++;
             }
         }
       }
       first++;        
   }
   for( int i = 1 ; i <= N ; i++)
     for( int j = 1 ; j<=M ; j++ )
     {
          if( map[i][j]=='@'&&step[0][i][j]!=-1&&step[1][i][j]!=-1 )//判断该点是否合法 
          {
             if( step[0][i][j]+step[1][i][j]<min )
               min = step[0][i][j]+step[1][i][j];
//               printf( "%d %d\n",step[0][i][j],step[1][i][j] );         
          }        
     }
   return min*11; 
}
int main( )
{
     int x1,y1,x2,y2;
     while( scanf( "%d%d",&N, &M )==2 )
     {
         memset( map , 0 ,sizeof( map ) );
         memset( step , -1 ,sizeof( step ) );
         for( int i = 1 ; i<= N ; i++ )
         {
             scanf( "%s", map[i]+1 );
             for( int j = 1 ; j<=M  ; j++ )
             {
                  if( map[i][j]=='M' )
                  {
                     x1 = i;
                     y1 = j;    
                  }        
                  else if( map[i][j]=='Y' )
                  {
                     x2 = i;
                     y2 = j;    
                  }
             }        
         }        
         printf( "%d\n",BFS( x1, y1 ,x2 ,y2 ) );
     }
     return 0;    
}