5.2.2 Electric Fences 电网

5.2.2 Electric Fences 电网

/*
PROG: fence3
LANG: C++
*/

#include < iostream >
#include < cmath >
using   namespace  std;

typedef  struct {
     int  x,y;
}Point;
int  N;
Point a[ 151 ][ 2 ];
double  ans,ax,ay;
void  swap(Point x,Point y){
    Point tmp = x;
    x = y;
    y = tmp;
}
void  init()
{
    scanf( " %d " , & N);
     for ( int  i = 1 ;i <= N; ++ i){
        scanf( " %d%d%d%d " , & a[i][ 0 ].x, & a[i][ 0 ].y, & a[i][ 1 ].x, & a[i][ 1 ].y);
         if (a[i][ 0 ].x > a[i][ 1 ].x || a[i][ 0 ].y > a[i][ 1 ].y)
            swap(a[i][ 0 ],a[i][ 1 ]);
    }
}
inline  double  sqr( double  x){
     return  x * x;
}
inline  double  min( double  x, double  y){
     if (x > y)  return  y;
     return  x;
}
double  dist( double  x, double  y){   // 计算点到线的距离
     double  dis = 0 ;
     for ( int  i = 1 ;i <= N; ++ i)
         if (a[i][ 0 ].x < x && a[i][ 1 ].x > x)   // 在x轴上
            dis += abs(y - a[i][ 0 ].y);
         else   if (a[i][ 0 ].y < y && a[i][ 1 ].y > y)   // 在y轴上
            dis += abs(x - a[i][ 0 ].x);
         else  dis += min(sqrt(sqr(x - a[i][ 0 ].x) + sqr(y - a[i][ 0 ].y)),
                              sqrt(sqr(x - a[i][ 1 ].x) + sqr(y - a[i][ 1 ].y)));   // 找两端的最小值
     return  dis;
}
void  solve()
{
     double  d = 10 ;   // 精度
     double  dx = 0 ,dy = 0 ;
    ans = 0xFFFFFFF ;
     do {
         for ( int  i = 0 ;i <= 10 ; ++ i)
             for ( int  j = 0 ;j <= 10 ; ++ j){    // 枚举点走的距离
                 double  tmp = dist(dx + d * i,dy + d * j);
                 if (tmp < ans){
                    ans = tmp;
                    ax = dx + d * i;
                    ay = dy + d * j;
                }
            }
        dx = ax - d;
        dy = ay - d;
        d /= 5.0 ;
    } while (d >= 0.001 );
    printf( " %0.1lf %0.1lf %0.1lf\n " ,ax,ay,ans);
}
int  main()
{
    freopen( " fence3.in " , " r " ,stdin);
    freopen( " fence3.out " , " w " ,stdout);
    init();
    solve();
     return   0 ;
}