HDU1875 畅通工程再续 最小生成树

HDU1875 畅通工程再续 最小生成树

http://acm.hdu.edu.cn/showproblem.php?pid=1875

Kruscal最小生成树 注意对double类型的快排可不要写错了

#include < stdio.h >
#include < stdlib.h >
#include < math.h >
struct  road{
     int  x,y;
     double  v;
}r[ 5002 ];
struct  point{
     int  a,b;
}p[ 102 ];
int  cmp( const   void   * a, const   void   * b)
{
     struct  road  * aa = ( struct  road  * )a;
     struct  road  * bb = ( struct  road  * )b;
     return  aa -> v  >  bb -> v  ?   1 : - 1 ;
}
int  bin[ 102 ];
int  find( int  x)
{
     int  r = x;
     while (bin[r] != r)
        r = bin[r];
     int  y = x;
     while (bin[y] != y)
    {
        y = bin[y];
        bin[y] = r;
    }
     return  r;
}
int  main()
{
     int  t,n,i,j,num,cnt;
     double  ans;
    scanf( " %d " , & t);
     while (t -- )
    {
        scanf( " %d " , & n);
         for (i = 0 ;i < n;i ++ )
            scanf( " %d%d " , & p[i].a, & p[i].b);
        num = 0 ;
         for (i = 0 ;i < n - 1 ;i ++ )
             for (j = i + 1 ;j < n;j ++ ){
                r[num].x = i,  r[num].y = j;
                r[num].v = sqrt( 1.0 * (p[i].a - p[j].a) * (p[i].a - p[j].a) + (p[i].b - p[j].b) * (p[i].b - p[j].b));
                num ++ ;
            }
         for (i = 0 ;i < n;i ++ )
            bin[i] = i;
        qsort(r,num, sizeof (r[ 0 ]),cmp);
        i = 0 ; ans = 0 ; cnt = 0 ;
         while (r[i].v < 10 )
            i ++ ;
         for (;i < num  &&  cnt < n - 1 ;i ++ )
        {
             if (r[i].v > 1000 )  break ;
             int  fx = find(r[i].x), fy = find(r[i].y);
             if (fx != fy)
            {
                bin[fx] = fy;
                cnt ++ ;
                ans += r[i].v;
            }
        }
         if (cnt == n - 1 )
            printf( " %.1lf\n " ,ans * 100 );
         else
            printf( " oh!\n " );
    }
     return   0 ;
}