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double xmult(double x1,double y1,double x2,double y2,double x0,double y0)

是算叉乘的 double area_triangle(double x1,double y1,double x2,double y2,double x3,double y3) 是算面积的 double dis_ptoline(double x1,double y1,double x2,double y2,double ex,double ey,double *px,double *py) 自己编的 算点到线段距离的

double xmult(double x1,double y1,double x2,double y2,double x0,double y0){    return (x1-x0)*(y2-y0)-(x2-x0)*(y1-y0);}double area_triangle(double x1,double y1,double x2,double y2,double x3,double y3){    return fabs(xmult(x1,y1,x2,y2,x3,y3))/2;}double dis_ptoline(double x1,double y1,double x2,double y2,double ex,double ey,double *px,double *py){ //第一个点，第二个点，目标点  ax ay为答案点  返回距离    double k,b,dis,tem1,tem2,t1,t2,yd=sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));    t2=sqrt((x2-ex)*(x2-ex)+(y2-ey)*(y2-ey));    t1=sqrt((x1-ex)*(x1-ex)+(y1-ey)*(y1-ey));    dis=area_triangle(x1,y1,x2,y2,ex,ey)*2/yd;    tem1=sqrt(t1*t1-dis*dis);    tem2=sqrt(t2*t2-dis*dis);        if (tem1>yd||tem2>yd) {        if (t1>t2) {*px=x2;*py=y2;return t2;}        else {*px=x1;*py=y1;return t1;}    }    *px=x1+(x2-x1)*tem1/yd;    *py=y1+(y2-y1)*tem1/yd;    return dis;}

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