Triangle.cpp


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#include "Triangle.h"
#include <math.h>


Triangle::Direction Triangle::getDirection() const {
  double c = (va.getX()-vb.getX())*(vc.getY()-vb.getY()) - (vc.getX()-vb.getX())*(va.getY()-vb.getY());
  
  return (c < 0) ? CW : (c > 0) ? CCW : Unknown;
}

double Triangle::area() const {
  double a = vb.distanceSq(vc);
  double b = vc.distanceSq(va);
  double c = va.distanceSq(vb);
  
  return sqrt((a+b+c)*a+b+c - 2*(a*a+b*b+c*c))/4;
}

double Triangle::perimeter() const {
  return va.distance(vb) + vb.distance(vc) + vc.distance(va);
}

bool Triangle::contains(const Vertex &v) const {
  double a = (v.getX()-vb.getX())*(vc.getY()-vb.getY()) - (vc.getX()-vb.getX())*(v.getY()-vb.getY());
  double b = (v.getX()-vc.getX())*(va.getY()-vc.getY()) - (va.getX()-vc.getX())*(v.getY()-vc.getY());
  double c = (v.getX()-va.getX())*(vb.getY()-va.getY()) - (vb.getX()-va.getX())*(v.getY()-va.getY());
  
  switch(getDirection()) {
    case CW:
      return ((a < 0) && (b < 0) && (c < 0));
    case CCW:
      return ((a > 0) && (b > 0) && (c > 0));
  }
  
  return false;
}