详细见https://blog.csdn.net/islittlehappy/article/details/81533090
准备的变量和函数 struct Point{double x,y;Point(){}Point(double xx,double yy){x=xx;y=yy;}};Point operator+(Point a,Point b){ //向量加 return Point(a.x+b.x,a.y+b.y); } Point operator-(Point a,Point b){ //向量减return Point(a.x-b.x,a.y-b.y);} double sqr(double x){return x*x;}double dis(Point a,Point b){ //求ab的长度 return sqrt(sqr(a.x-b.x)+sqr(a.y-b.y));} 重心 Point gravity(Point a,Point b,Point c){ // 重心 double x=(a.x+b.x+c.x)/3;double y=(a.y+b.y+c.y)/3;return Point(x,y);} 内心 Point Incenter(Point a,Point b,Point c){ //三角形内心 double A=dis(b,c); double B=dis(a,c); double C=dis(a,b); double S=A+B+C; double x=(A*a.x+B*b.x+C*c.x)/S; double y=(A*a.y+B*b.y+C*c.y)/S; return Point(x,y);} 外心 Point Circum(Point a,Point b,Point c){ //三角形外心 double x1=a.x,y1=a.y;double x2=b.x,y2=b.y;double x3=c.x,y3=c.y;double a1=2*(x2-x1);double b1=2*(y2-y1);double c1=x2*x2+y2*y2-x1*x1-y1*y1;double a2=2*(x3-x2);double b2=2*(y3-y2);double c2=x3*x3+y3*y3-x2*x2-y2*y2;double x=(c1*b2-c2*b1)/(a1*b2-a2*b1);double y=(a1*c2-a2*c1)/(a1*b2-a2*b1);return Point(x,y);} 垂心 Point ortho(Point a,Point b,Point c){ //垂心 double A1=b.x-c.x;double B1=b.y-c.y;double C1=A1*a.y-B1*a.x;double A2=a.x-c.x;double B2=a.y-c.y;double C2=A2*b.y-B2*b.x;double x=(A1*C2-A2*C1)/(A2*B1-A1*B2);double y=(B1*C2-B2*C1)/(A2*B1-A1*B2);return Point(x,y);}