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#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define fbo find_by_order
#define ook order_of_key
typedef long long ll;
typedef pair<ll,ll> ii;
typedef vector<int> vi;
typedef long double ld;
typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update> pbds;
typedef set<ll>::iterator sit;
typedef map<ll,ll>::iterator mit;
const double eps=1e-8;
const double pi=acos(-1.0);
const double inf=1e20;
const int maxp=111111;
int dblcmp(double d)
{
if (fabs(d)<eps)return 0;
return d>eps?1:-1;
}
inline double sqr(double x){return x*x;}
struct point
{
double x,y;
point(){}
point(double _x,double _y):
x(_x),y(_y){};
void input()
{
scanf("%lf%lf",&x,&y);
}
void output()
{
printf("%.2f %.2f\n",x,y);
}
bool operator==(point a)const
{
return dblcmp(a.x-x)==0&&dblcmp(a.y-y)==0;
}
bool operator<(point a)const
{
return dblcmp(a.x-x)==0?dblcmp(y-a.y)<0:x<a.x;
}
double len()
{
return hypot(x,y);
}
double len2()
{
return x*x+y*y;
}
double distance(point p)
{
return hypot(x-p.x,y-p.y);
}
point add(point p)
{
return point(x+p.x,y+p.y);
}
point sub(point p)
{
return point(x-p.x,y-p.y);
}
point mul(double b)
{
return point(x*b,y*b);
}
point div(double b)
{
return point(x/b,y/b);
}
double dot(point p)
{
return x*p.x+y*p.y;
}
double det(point p)
{
return x*p.y-y*p.x;
}
double rad(point a,point b)
{
point p=*this;
return fabs(atan2(fabs(a.sub(p).det(b.sub(p))),a.sub(p).dot(b.sub(p))));
}
point trunc(double r)
{
double l=len();
if (!dblcmp(l))return *this;
r/=l;
return point(x*r,y*r);
}
point rotleft()
{
return point(-y,x);
}
point rotright()
{
return point(y,-x);
}
point rotate(point p,double angle)//绕点p逆时针旋转angle角度
{
point v=this->sub(p);
double c=cos(angle),s=sin(angle);
return point(p.x+v.x*c-v.y*s,p.y+v.x*s+v.y*c);
}
};
struct line
{
point a,b;
line(){}
line(point _a,point _b)
{
a=_a;
b=_b;
}
bool operator==(line v)
{
return (a==v.a)&&(b==v.b);
}
//倾斜角angle
line(point p,double angle)
{
a=p;
if (dblcmp(angle-pi/2)==0)
{
b=a.add(point(0,1));
}
else
{
b=a.add(point(1,tan(angle)));
}
}
//ax+by+c=0
line(double _a,double _b,double _c)
{
if (dblcmp(_a)==0)
{
a=point(0,-_c/_b);
b=point(1,-_c/_b);
}
else if (dblcmp(_b)==0)
{
a=point(-_c/_a,0);
b=point(-_c/_a,1);
}
else
{
a=point(0,-_c/_b);
b=point(1,(-_c-_a)/_b);
}
}
void input()
{
a.input();
b.input();
}
void adjust()
{
if (b<a)swap(a,b);
}
double length()
{
return a.distance(b);
}
double angle()//直线倾斜角 0<=angle<180
{
double k=atan2(b.y-a.y,b.x-a.x);
if (dblcmp(k)<0)k+=pi;
if (dblcmp(k-pi)==0)k-=pi;
return k;
}
//点和线段关系
//1 在逆时针
//2 在顺时针
//3 平行
int relation(point p)
{
int c=dblcmp(p.sub(a).det(b.sub(a)));
if (c<0)return 1;
if (c>0)return 2;
return 3;
}
bool pointonseg(point p)
{
return dblcmp(p.sub(a).det(b.sub(a)))==0&&dblcmp(p.sub(a).dot(p.sub(b)))<=0;
}
bool parallel(line v)
{
return dblcmp(b.sub(a).det(v.b.sub(v.a)))==0;
}
//2 规范相交
//1 非规范相交
//0 不相交
int segcrossseg(line v)
{
int d1=dblcmp(b.sub(a).det(v.a.sub(a)));
int d2=dblcmp(b.sub(a).det(v.b.sub(a)));
int d3=dblcmp(v.b.sub(v.a).det(a.sub(v.a)));
int d4=dblcmp(v.b.sub(v.a).det(b.sub(v.a)));
if ((d1^d2)==-2&&(d3^d4)==-2)return 2;
return (d1==0&&dblcmp(v.a.sub(a).dot(v.a.sub(b)))<=0||
d2==0&&dblcmp(v.b.sub(a).dot(v.b.sub(b)))<=0||
d3==0&&dblcmp(a.sub(v.a).dot(a.sub(v.b)))<=0||
d4==0&&dblcmp(b.sub(v.a).dot(b.sub(v.b)))<=0);
}
int linecrossseg(line v)//*this seg v line
{
int d1=dblcmp(b.sub(a).det(v.a.sub(a)));
int d2=dblcmp(b.sub(a).det(v.b.sub(a)));
if ((d1^d2)==-2)return 2;
return (d1==0||d2==0);
}
//0 平行
//1 重合
//2 相交
int linecrossline(line v)
{
if ((*this).parallel(v))
{
return v.relation(a)==3;
}
return 2;
}
point crosspoint(line v)
{
double a1=v.b.sub(v.a).det(a.sub(v.a));
double a2=v.b.sub(v.a).det(b.sub(v.a));
return point((a.x*a2-b.x*a1)/(a2-a1),(a.y*a2-b.y*a1)/(a2-a1));
}
double dispointtoline(point p)
{
return fabs(p.sub(a).det(b.sub(a)))/length();
}
double dispointtoseg(point p)
{
if (dblcmp(p.sub(b).dot(a.sub(b)))<0||dblcmp(p.sub(a).dot(b.sub(a)))<0)
{
return min(p.distance(a),p.distance(b));
}
return dispointtoline(p);
}
point lineprog(point p)
{
return a.add(b.sub(a).mul(b.sub(a).dot(p.sub(a))/b.sub(a).len2()));
}
point symmetrypoint(point p)
{
point q=lineprog(p);
return point(2*q.x-p.x,2*q.y-p.y);
}
};
bool clash(line a, line b)
{
return (a.segcrossseg(b)!=0);
}
bool clash2(line a, line b)
{
if(a.segcrossseg(b)!=0)
{
if(a.parallel(b)) return false;
point tmp = a.crosspoint(b);
////cerr<<"CROSSPOINT : \n"<<a.a.x<<' '<<a.a.y<<' '<<a.b.x<<' '<<a.b.y<<'\n'<<b.a.x<<' '<<b.a.y<<' '<<b.b.x<<' '<<b.b.y<<'\n'<<tmp.x<<' '<<tmp.y<<'\n';
if(b.a == tmp || b.b == tmp || a.a == tmp || a.b == tmp) return false;
return true;
}
return false;
}
const int N = 412;
point a[N+11];
point b[N+11];
point square[4];
ld dist[N+11][N+11];
line ray;
void amin(ld &x, ld y)
{
x=min(x,y);
}
void add_edge(int u, int v, ld d, bool intersect)
{
u*=2; v*=2;
if(intersect) //if u-v intersects the ray
{
for(int i=0;i<2;i++)
{
amin(dist[u][v^1],d); amin(dist[u^1][v],d);
swap(u,v);
}
}
else
{
for(int i=0;i<2;i++)
{
amin(dist[u][v],d); amin(dist[u^1][v^1],d);
swap(u,v);
}
}
}
int n,s;
bool good(point a, point b)
{
for(int i=0;i<4;i++)
{
if(clash2(line(a,b), line(square[i],square[(i+1)%4]))) return false;
}
point tmp = point((a.x+b.x)*0.5, (a.y+b.y)*0.5); //check if the line segment lies within the square
if(tmp.x>-s&&tmp.x<s&&tmp.y>-s&&tmp.y<s) return false;
return true;
}
ld getdist(point a, point b)
{
return a.distance(b);
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
cin>>n>>s; ld ans = s*8;
square[0] = point(-s,-s);
square[1] = point(-s, s);
square[2] = point(s,s);
square[3] = point(s,-s);
ray = line(point(0,0), point(1,2018));
for(int i=0;i<n;i++)
{
cin>>a[i].x>>a[i].y>>b[i].x>>b[i].y;
}
for(int i=0;i<4;i++)
{
a[n] = square[i];
b[n++] = square[i];
}
for(int i=0;i<N;i++)
{
for(int j=0;j<N;j++)
{
dist[i][j]=(i==j?0.0:ld(1e12));
}
}
for(int i=0;i<n;i++)
{
add_edge(i,i+n,0,clash(ray, line(a[i], b[i])));
for(int j=i+1;j<n;j++)
{
if(good(a[i],a[j]))
{
//cerr<<"DO ZZZ "<<i<<' '<<j<<'\n';
//cerr<<"LINE : "<<a[i].x<<' '<<a[i].y<<' '<<a[j].x<<' '<<a[j].y<<'\n';
add_edge(i,j,getdist(a[i],a[j]),clash(ray,line(a[i],a[j])));
}
if(good(a[i],b[j]))
{
//cerr<<"DO ZZZ "<<i<<' '<<j+n<<'\n';
//cerr<<"LINE : "<<a[i].x<<' '<<a[i].y<<' '<<b[j].x<<' '<<b[j].y<<'\n';
add_edge(i,j+n,getdist(a[i],b[j]),clash(ray,line(a[i],b[j])));
}
if(good(b[i],a[j]))
{
//cerr<<"DO ZZZ "<<i+n<<' '<<j<<'\n';
//cerr<<"LINE : "<<b[i].x<<' '<<b[i].y<<' '<<a[j].x<<' '<<a[j].y<<'\n';
add_edge(i+n,j,getdist(b[i],a[j]),clash(ray,line(b[i],a[j])));
}
if(good(b[i],b[j]))
{
//cerr<<"DO ZZZ "<<i+n<<' '<<j+n<<'\n';
//cerr<<"LINE : "<<b[i].x<<' '<<b[i].y<<' '<<b[j].x<<' '<<b[j].y<<'\n';
add_edge(i+n,j+n,getdist(b[i],b[j]),clash(ray,line(b[i],b[j])));
}
for(int z=0;z<2;z++)
{
//if(j<n-4)
//{
point foot = line(a[j], b[j]).lineprog(a[i]);
if(line(a[j], b[j]).pointonseg(foot) && good(foot, a[i]))
{
//cerr<<"DO "<<i<<' '<<j<<' '<<j+n<<'\n';
add_edge(i, j, getdist(a[i], foot), clash(ray, line(a[i], foot))^clash(ray, line(a[j], foot)));
add_edge(i, j + n, getdist(a[i], foot), clash(ray, line(a[i], foot))^clash(ray, line(b[j], foot)));
}
foot = line(a[j], b[j]).lineprog(b[i]);
if(line(a[j], b[j]).pointonseg(foot) && good(foot, b[i]))
{
//cerr<<"DO "<<i+n<<' '<<j<<' '<<j+n<<'\n';
add_edge(i + n, j, getdist(b[i], foot), clash(ray, line(b[i], foot))^clash(ray, line(a[j], foot)));
add_edge(i + n, j + n, getdist(b[i], foot), clash(ray, line(b[i], foot))^clash(ray, line(b[j], foot)));
}
//}
swap(i,j);
}
}
}
for(int i=0;i<4*n;i++)
{
for(int j=0;j<4*n;j++)
{
//if(dist[i][j]<ld(1e12)) cerr<<"("<<i/2<<","<<i%2<<") ("<<j/2<<","<<j%2<<") "<<dist[i][j]<<'\n';
}
}
for(int k=0;k<4*n;k++)
{
for(int i=0;i<4*n;i++)
{
for(int j=0;j<4*n;j++)
{
amin(dist[i][j],dist[i][k]+dist[k][j]);
}
}
}
for(int i=0;i<2*n;i++)
{
//cerr<<"DIST : "<<i*2<<' '<<i*2+1<<' '<<dist[i*2][i*2+1]<<'\n';
amin(ans, dist[i*2][i*2+1]);
}
cout<<fixed<<setprecision(10)<<ans<<'\n';
}
컴파일 시 표준 에러 (stderr) 메시지
fences.cpp: In member function 'int line::segcrossseg(line)':
fences.cpp:213:22: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
return (d1==0&&dblcmp(v.a.sub(a).dot(v.a.sub(b)))<=0||
~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fences.cpp:215:22: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
d3==0&&dblcmp(a.sub(v.a).dot(a.sub(v.b)))<=0||
~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fences.cpp:216:22: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
d4==0&&dblcmp(b.sub(v.a).dot(b.sub(v.b)))<=0);
~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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