poj 2850 Stacking Cylinders

poj 2850 Stacking Cylinders

读懂题后其实就是一道数学题了
hit: The distance between adjacent centers will be at least 2.0 (so the cylinders do not overlap) and at most 3.4...
3.4=1+1+1.4，1.4=sqrt(2);

#include  < stdio.h >
#include  < math.h >

double  num[ 20 ][ 20 ], numy[ 20 ][ 20 ];

int  n;

void  getpoint(  double  x1,  double  y1,  double  x2,  double  y2 ,  double   &  x,  double   &  y )
{
     double  a, b, c, d, e, f;
    a =  x2 - x1;
    b =  y2 - y1;
    c =  (x1 + x2) / 2.0 ;
    d =  (y1 + y2) / 2.0 ;
    e =  (y1 - y2) / 2.0 ;
    f =  (x1 - x2) / 2.0 ;
    y = sqrt( ( 4 - e * e - f * f) * a * a / (a * a + b * b) )  +  d;
    x =  ( b * ( d - y ) / a ) + c;
}

int  main()
{
    scanf( " %d " ,  & n);
     for  (  int  l =   1 ; l  <=  n; l ++  )
    {
         int  t;
        scanf( " %d " ,  & t);
         int  i, j;
         for  ( i  =   0 ; i  <  t ; i ++  )
        {
            scanf( " %lf " , num[t - 1 ] + i);
            numy[t - 1 ][i] = 1.0 ;
        }
         for  ( j  =  t - 1 ; j  >   0  ; j --  )
        {
             for  ( i  =   0 ; i  <  t; i ++  )
            {
                getpoint(num[j][i], numy[j][i], num[j][i + 1 ], numy[j][i + 1 ], num[j - 1 ][i], numy[j - 1 ][i]);
            }
        }
        printf( " %d: %.4f %.4f\n " , l, num[ 0 ][ 0 ], numy[ 0 ][ 0 ]);
    }
     return   0 ;
}