c++ strchr函数_strchr函数返回_模拟实现strchr函数(39)

returnret;

}

int intersect_line_circle(point c,doubler,point l1,point l2){

returndisptoline(c,l1,l2)<reps;

}

int intersect_seg_circle(point c,doubler,point l1,point l2){

doublet1=distance(c,l1)-r,t2=distance(c,l2)-r;

pointt=c;

if(t1<eps||t2<eps)

return t1>-eps||t2>-eps;

t.x=l1.y-l2.y;

t.y=l2.x-l1.x;

returnxmult(l1,c,t)*xmult(l2,c,t)<eps&&disptoline(c,l1,l2)-r<eps;

}

int intersect_circle_circle(point c1,doubler1,point c2,double r2){

returndistance(c1,c2)<r1r2eps&&distance(c1,c2)>fabs(r1-r2)-eps;

}

point dot_to_circle(point c,double r,pointp){

pointu,v;

if(distance(p,c)<eps)

return p;

u.x=c.xr*fabs(c.x-p.x)/distance(c,p);

u.y=c.yr*fabs(c.y-p.y)/distance(c,p)*((c.x-p.x)*(c.y-p.y)<0?-1:1);

v.x=c.x-r*fabs(c.x-p.x)/distance(c,p);

v.y=c.y-r*fabs(c.y-p.y)/distance(c,p)*((c.x-p.x)*(c.y-p.y)<0?-1:1);

returndistance(u,p)<distance(v,p)?u:v;

}

//计算线段与圆的交点可用这个函数后判点是否段上

void intersection_line_circle(pointc,double r,point l1,point l2,point& p1,point& p2){

pointp=c;

doublet;

p.x=l1.y-l2.y;

p.y=l2.x-l1.x;

p=intersection(p,c,l1,l2);

t=sqrt(r*r-distance(p,c)*distance(p,c))/distance(l1,l2);

p1.x=p.x(l2.x-l1.x)*t;

p1.y=p.y(l2.y-l1.y)*t;

p2.x=p.x-(l2.x-l1.x)*t;

p2.y=p.y-(l2.y-l1.y)*t;

}

void intersection_circle_circle(pointc1,double r1,point c2,double r2,point& p1,point& p2){

pointu,v;

doublet;

t=(1(r1*r1-r2*r2)/distance(c1,c2)/distance(c1,c2))/2;

u.x=c1.x(c2.x-c1.x)*t;

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