c++ strchr函数_strchr函数返回_模拟实现strchr函数(29)

returnfabs(xmult(p,l.a,l.b))/distance(l.a,l.b);

}

double disptoseg(point p,point l1,pointl2){

pointt=p;

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

if(xmult(l1,t,p)*xmult(l2,t,p)>eps)

returndistance(p,l1)<distance(p,l2)?distance(p,l1):distance(p,l2);

returnfabs(xmult(p,l1,l2))/distance(l1,l2);

}

point rotate(point v,point p,doubleangle,double scale){

pointret=p;

v.x-=p.x,v.y-=p.y;

p.x=scale*cos(angle);

p.y=scale*sin(angle);

ret.x=v.x*p.x-v.y*p.y;

ret.y=v.x*p.yv.y*p.x;

returnret;

}

#include <math.h>

struct point{double x,y;};

double xmult(point p1,point p2,point p0){

return(p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y);

}

double xmult(double x1,double y1,doublex2,double y2,double x0,double y0){

return(x1-x0)*(y2-y0)-(x2-x0)*(y1-y0);

}

double area_(point p1,pointp2,point p3){

returnfabs(xmult(p1,p2,p3))/2;

}

double area_(double x1,doubley1,double x2,double y2,double x3,double y3){

returnfabs(xmult(x1,y1,x2,y2,x3,y3))/2;

}

double area_(double a,doubleb,double c){

doubles=(abc)/2;

returnsqrt(s*(s-a)*(s-b)*(s-c));

}

double area_polygon(int n,point* p){

doubles1=0,s2=0;

inti;

for(i=0;i<n;i)

s1=p[(i1)%n].y*p[i].x,s2=p[(i1)%n].y*p[(i2)%n].x;

returnfabs(s1-s2)/2;

}

#include <math.h>

const double pi=acos(-1);

//返回两点所在大圆劣弧对应圆心角,0<=angle<=pi

double angle(double lng1,double lat1,doublelng2,double lat2){

doubledlng=fabs(lng1-lng2)*pi/180;

while(dlng>=pipi)

dlng-=pipi;

if(dlng>pi)

dlng=pipi-dlng;

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