c++ strchr函数_strchr函数返回_模拟实现strchr函数(31)

returnintersection(u,v);

}

point perpencenter(point a,point b,pointc){

lineu,v;

u.a=c;

u.b.x=u.a.x-a.yb.y;

u.b.y=u.a.ya.x-b.x;

v.a=b;

v.b.x=v.a.x-a.yc.y;

v.b.y=v.a.ya.x-c.x;

returnintersection(u,v);

}

//到三角形三顶点距离的平方和最小的点

//三角形内到三边距离之积最大的点

point barycenter(point a,point b,point c){

lineu,v;

u.a.x=(a.xb.x)/2;

u.a.y=(a.yb.y)/2;

u.b=c;

v.a.x=(a.xc.x)/2;

v.a.y=(a.yc.y)/2;

v.b=b;

returnintersection(u,v);

}

point fermentpoint(point a,point b,pointc){

pointu,v;

doublestep=fabs(a.x)fabs(a.y)fabs(b.x)fabs(b.y)fabs(c.x)fabs(c.y);

inti,j,k;

u.x=(a.xb.xc.x)/3;

u.y=(a.yb.yc.y)/3;

while(step>1e-10)

for (k=0;k<10;step/=2,k)

for(i=-1;i<=1;i)

for (j=-1;j<=1;j){

v.x=u.xstep*i;

v.y=u.ystep*j;

if(distance(u,a)distance(u,b)distance(u,c)>distance(v,a)distance(v,b)distance(v,c))

u=v;

}

returnu;

}

//三维几何函数库

#include <math.h>

#define eps 1e-8

#define zero(x)(((x)>0?(x):-(x))<eps)

struct point3{double x,y,z;};

struct line3{point3 a,b;};

struct plane3{point3 a,b,c;};

point3 xmult(point3 u,point3 v){

point3ret;

ret.x=u.y*v.z-v.y*u.z;

ret.y=u.z*v.x-u.x*v.z;

ret.z=u.x*v.y-u.y*v.x;

returnret;

}

double dmult(point3 u,point3 v){

returnu.x*v.xu.y*v.yu.z*v.z;

}

point3 subt(point3 u,point3 v){

point3ret;

ret.x=u.x-v.x;

ret.y=u.y-v.y;

ret.z=u.z-v.z;

returnret;

}

point3 pvec(plane3 s){

returnxmult(subt(s.a,s.b),subt(s.b,s.c));

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