POJ 2965 The Pilots Brothers' refrigerator

POJ 2965 The Pilots Brothers' refrigerator

与POJ 1753类似，但是需要加点优化，这里主要使用了位运算的方法。

#include < cstdio >
#include < cstring >
#define  g(x,y) (((x-1)<<2)+y)
using   namespace  std;

int  a,d;
int  ansn,ans;

void  f( int  i, int   & x, int   & y)
{
    x = i / 4 + 1 ;
    y = i % 4 ;
     if (i % 4 == 0 )
    {
        x -- ;
        y = 4 ;
    }
}

void  handle( int   & r, int  x, int  y)
{
     for ( int  i = 1 ;i <= 4 ;i ++ )
    {
        r ^= ( 1 << g(x,i));
        r ^= ( 1 << g(i,y));
    }
    r ^= ( 1 << g(x,y));
}

void  dfs( int  last, int  have)
{
     if (have >= ansn)
         return ;

     int  r(a);
     for ( int  i = 1 ;i <= 16 ;i ++ )
         if (d & ( 1 << i))
        {
             int  x,y;
            f(i,x,y);
            handle(r,x,y);
        }
     if (r == 0 )
    {
        ansn = have;
        ans = d;
    }

     for ( int  i = last + 1 ;i <= 16 ;i ++ )
    {
        d = (d | ( 1 << i));
        dfs(i,have + 1 );
        d = ( ~ (( ~ d) | ( 1 << i)));
    }
}

int  main()
{
     /*
    freopen("data.in","r",stdin);
    freopen("data.out","w",stdout);
    // */

    a = 0 ;
     for ( int  i = 1 ;i <= 4 ;i ++ )
    {
         for ( int  j = 1 ;j <= 4 ;j ++ )
        {
             char  t;
            scanf( " %c " , & t);
             if (t == ' + ' )
                a = (a | ( 1 << g(i,j)));
             else
                a = ( ~ (( ~ a) | ( 1 << g(i,j))));
        }
        getchar();
    }

    ansn = 0x7f7f7f7f ;
    d = 0 ;
    dfs( 0 , 0 );

    printf( " %d\n " ,ansn);
     for ( int  i = 1 ;i <= 16 ;i ++ )
         if (ans & ( 1 << i))
        {
             int  x,y;
            f(i,x,y);
            printf( " %d %d\n " ,x,y);
        }

     return   0 ;
}