poj 2312 Battle City

poj 2312 Battle City

http://acm.pku.edu.cn/JudgeOnline/problem?id=2312
poj 2312 Battle City

简单的BFS

Source Code

Problem: 2312		User: lovecanon
Memory: 1244K		Time: 16MS
Language: GCC		Result: Accepted

#include < stdio.h >
typedef  struct  node 
{
     int  x;
     int  y;
}node;
node Q[ 100000 ];
char  board[ 301 ][ 301 ];
int  step[ 301 ][ 301 ];
int  m,n;
const   int  dx[] = { 0 , 0 , - 1 , 1 },dy[] = { - 1 , 1 , 0 , 0 };

int  ok( int  x, int  y)
{
     if (x >= 0 && x < m && y >= 0 && y < n)  return   1 ;
     else   return   0 ;
}

void  solve( int  x1, int  y1, int  x2, int  y2)
{
     int  i,j,cntx,cnty,nextx,nexty,head,tail,tmp,minstep = 0x7fffffff ;
    cntx = x1;cnty = y1;head = tail = 0 ;
     for (i = 0 ;i < m;i ++ )
         for (j = 0 ;j < n;j ++ )
            step[i][j] = 0x7fffffff ;
    step[cntx][cnty] = 0 ;

     while ( 1 )
    {
         for (i = 0 ;i < 4 ;i ++ )
        {
            nextx = cntx + dx[i];
            nexty = cnty + dy[i];
             if (ok(nextx,nexty))
            {
                 if (board[nextx][nexty] == ' E ' )
                {
                    tmp = step[cntx][cnty] + 1 ;
                     if (tmp < step[nextx][nexty])
                    {
                        step[nextx][nexty] = tmp;
                        Q[ ++ tail].x = nextx;
                        Q[tail].y = nexty;
                    }
                }
                 if (board[nextx][nexty] == ' B ' )
                {
                    tmp = step[cntx][cnty] + 2 ;
                     if (tmp < step[nextx][nexty])
                    {
                        step[nextx][nexty] = tmp;
                        Q[ ++ tail].x = nextx;
                        Q[tail].y = nexty;
                    }
                }
                 if (board[nextx][nexty] == ' T ' )
                {
                     if (step[cntx][cnty] + 1 < minstep)  minstep = step[cntx][cnty] + 1 ;
                }
            }
        }
         if (head == tail)   break ;
         else
        {
            cntx = Q[ ++ head].x;
            cnty = Q[head].y;
        }
 
    }
     if (minstep == 0x7fffffff )  printf( " -1\n " );
     else  printf( " %d\n " ,minstep);

}

int  main()
{
     while ( 1 )
    {
         int  i,j;
         int  x1,y1,x2,y2;

        scanf( " %d%d " , & m, & n);
        getchar();

         if (m == 0 && n == 0 )  return   0 ;

         for (i = 0 ;i < m;i ++ )
        {
             for (j = 0 ;j < n;j ++ )
            {
                board[i][j] = getchar();
                 if (board[i][j] == ' Y ' )
                {
                    x1 = i;y1 = j;
                }
                 if (board[i][j] == ' T ' )
                {
                    x2 = i;y2 = j;
                }
            }
            getchar();
        }
        solve(x1,y1,x2,y2);
    }
     return   0 ;

}