版权声明:本文为博主原创文章,未经博主允许不得转载。 https://blog.csdn.net/Game_Acm/article/details/82589337
const double eps = 1e-8;
const double pi = acos(-1.0);
//判浮点数符号
int sgn( double x )
{
if ( fabs(x)<eps ) return 0;
if ( x<0 ) return -1;
if ( x>0 ) return 1;
}
//Point定义
struct Point
{
double x,y;
Point(){}
Point( double _x , double _y )
{
x = _x; y = _y;
}
Point operator -( const Point&b )const
{
return Point( x-b.x , y-b.y );
}
Point operator +( const Point&b )const
{
return Point( x+b.x , y+b.y );
}
//叉积
//叉积>0,a在b的顺时针方向
//叉积<0,a在b的逆时针方向
//叉积=0,a与b平行
double operator ^( const Point&b )const
{
return x*b.y-y*b.x;
}
//点积
double operator *( const Point&b )const
{
return x*b.x+y*b.y;
}
//绕原点旋转角度B(弧度制)后x,y的变化
void transXY( double B )
{
double tx = x,ty = y;
x = tx*cos(B)-ty*sin(B);
y = tx*sin(B)+ty*cos(B);
}
};
//Line定义
struct Line
{
Point s,e;
Line(){}
Line( Point _s , Point _e )
{
s = _s; e = _e;
}
//求两直线交点
//第一个值为0表示直线重合,为1表示直线平行,为2表示直线相交
pair<int,Point> operator &( const Line&b )const
{
Point res = s;
if ( sgn((s-e)^(b.s-b.e))==0 )
{
if ( sgn((s-b.e)^(b.s-b.e))==0 )
return make_pair( 0 , res );
else
return make_pair( 1 , res );
}
double t = ((s-b.s)^(b.s-b.e))/((s-e)^(b.s-b.e));
res.x += (e.x-s.x)*t;
res.y += (e.y-s.y)*t;
return make_pair( 2 , res );
}
};
//两点间距离
double dist( Point a , Point b )
{
return sqrt( (a-b)*(a-b) );
}
//判断线段相交
bool inter( Line l1 , Line l2 )
{
return
max( l1.s.x , l1.e.x )>=min( l2.s.x , l2.e.x )&&
max( l2.s.x , l2.e.x )>=min( l1.s.x , l1.e.x )&&
max( l1.s.y , l1.e.y )>=min( l2.s.y , l2.e.y )&&
max( l2.s.y , l2.e.y )>=min( l1.s.y , l1.e.y )&&
sgn((l2.s-l1.e)^(l1.s-l1.e))*sgn((l2.e-l1.e)^(l1.s-l1.e))<=0&&
sgn((l1.s-l2.e)^(l2.s-l2.e))*sgn((l1.e-l2.e)^(l2.s-l2.e))<=0;
}
//判断直线L1和线段L2相交
//小心直线是单点的情况
bool Seg_inter_line( Line l1 , Line l2 )
{
return sgn((l2.s-l1.e)^(l1.s-l1.e))*sgn((l2.e-l1.e)^(l1.s-l1.e))<=0;
}
//点到直线距离,返回点到直线的最近点
Point PointToLine( Point P , Line L )
{
Point result;
double t = ((P-L.s)*(L.e-L.s))/((L.e-L.s)*(L.e-L.s));
result.x = L.s.x+(L.e.x-L.s.x)*t;
result.y = L.s.y+(L.e.y-L.s.y)*t;
return result;
}
//点到线段距离。返回点到线段的最近点
Point NearestPointToLineSeg( Point P , Line L )
{
Point result;
double t = ((P-L.s)*(L.e-L.s))/((L.e-L.s)*(L.e-L.s));
if ( t>=0&&t<=1 )
{
result.x = L.s.x+(L.e.x-L.s.x)*t;
result.y = L.s.y+(L.e.y-L.s.y)*t;
}
else
{
if( dist(P,L.s)<dist(P,L.e) ) result = L.s;
else result = L.e;
}
return result;
}
//计算多边形面积,点编号从0~n-1
double calcArea( Point p[] , int n )
{
double res = 0;
for ( int i=0 ; i<n ; i++ )
res += (p[i]^p[(i+1)%n])/2;
return fabs(res);
}
//判断点在线段上
bool OnSeg( Point P , Line L )
{
return
sgn((L.s-P)^(L.e-P))==0&&
sgn((P.x-L.s.x)*(P.x-L.e.x))<=0&&
sgn((P.y-L.s.y)*(P.y-L.e.y))<=0;
}
//判断点在凸多边形内
//点形成一个凸包,而且按逆时针排序(如果是顺时针把里面的<0改成>0)
//点的编号0~n-1
//返回-1表示点在凸多边形外
//返回 0表示点在凸多边形上
//返回 1表示点在凸多边形内
int inConvexPoly( Point a , Point p[] , int n )
{
for ( int i=0 ; i<n ; i++ )
{
if ( sgn((p[i]-a)^(p[(i+1)%n]-a))<0 ) return -1;
else if ( OnSeg(a,Line(p[i],p[(i+1)%n])) ) return 0;
}
return 1;
}
//判断点在任意多边形内
//射线法,poly[]的顶点数要大于等于3,点的编号0~n-1
//返回-1表示点在凸多边形外
//返回 0表示点在凸多边形上
//返回 1表示点在凸多边形内
int inPoly( Point p , Point poly[] , int n )
{
int cnt;
Line ray,side;
cnt = 0;
ray.s = p;
ray.e.y = p.y;
ray.e.x = -100000000000.0;//-INF
for ( int i=0 ; i<n ; i++ )
{
side.s = poly[i];
side.e = poly[(i+1)%n];
if ( OnSeg(p,side) ) return 0;
//如果平行轴则不考虑
if ( sgn(side.s.y-side.e.y)==0 ) continue;
if ( OnSeg(side.s,ray) )
{
if ( sgn(side.s.y-side.e.y)>0 ) cnt++;
}
else if ( OnSeg(side.e,ray) )
{
if ( sgn(side.e.y-side.s.y)>0 ) cnt++;
}
else if ( inter(ray,side) ) cnt++;
}
if ( cnt%2==1 ) return 1;
else return -1;
}
//判断凸多边形
//允许共线边
//点可以是顺时针给出也可以是逆时针给出
//点的编号0~n-1
bool isconvex( Point poly[] , int n )
{
bool s[3]; memset ( s , false , sizeof(s) );
for ( int i=0 ; i<n ; i++ )
{
s[sgn( (poly[(i+1)%n]-poly[i])^(poly[(i+2)%n]-poly[i]) )+1] = true;
if ( s[0]&&s[2] ) return false;
}
return true;
}