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#include "Polygon.h"
#include <math.h>
double Polygon::area() const {
double d = 0.0;
for(const_iterator it = begin(); it != end(); it++) {
const_iterator it2 = it+1;
if(it2 == end()) it2 = begin();
d += (it2->getX()+it->getX())*(it2->getY()-it->getY());
}
return fabs(d/2);
}
double Polygon::perimeter() const {
double d = 0.0;
for(const_iterator it = begin(); it != end(); it++) {
const_iterator it2 = it+1;
if(it2 == end()) it2 = begin();
d += it->distance(*it2);
}
return d;
}
int Polygon::quadrant(const Vertex &v) const {
if(v.getX() > 0 && v.getY() >= 0) return 1;
if(v.getX() >= 0 && v.getY() < 0) return 2;
if(v.getX() < 0 && v.getY() <= 0) return 3;
if(v.getX() <= 0 && v.getY() > 0) return 4;
return 0;
}
bool Polygon::contains(const Vertex &v) const {
int d = 0;
int q, ql, q2;
LINE d1 = {Vertex(-1, -1), Vertex(1, 1)};
LINE d2 = {Vertex(-1, 1), Vertex(1, -1)};
LINE l;
Vertex v2;
if(empty()) return false;
v2 = back() - v;
q = quadrant(v2);
if(q == 0) return true;
for(const_iterator it = begin(); it != end(); it++) {
ql = q;
v2 = *it - v;
q = quadrant(v2);
if(q == 0) return true;
switch(q-ql) {
case 0:
break;
case 1:
case -3:
d++;
break;
case 3:
case -1:
d--;
break;
default:
l.v1 = ((it == begin()) ? back() : *(it-1)) - v;
l.v2 = v2;
if(q == 1 || q == 3) {
if(!(lineIntersection(&l, &d2, &v2) & INTERSECTION_LINE)) return false;
q2 = quadrant(v2);
if(q2 == 0) return true;
if((q == 1 && q2 == 2) || (q == 3 && q2 == 4)) d -= 2;
else d += 2;
}
else {
if(!(lineIntersection(&l, &d1, &v2) & INTERSECTION_LINE)) return false;
q2 = quadrant(v2);
if(q2 == 0) return true;
if((q == 2 && q2 == 3) || (q == 4 && q2 == 1)) d -= 2;
else d += 2;
}
}
}
return (d != 0);
}
bool Polygon::intersects(const LINE *l) const {
LINE line;
for(Polygon::const_iterator it = begin(); it != end(); it++) {
Polygon::const_iterator it2 = it+1;
if(it2 == end()) it2 = begin();
line.v1 = *it;
line.v2 = *it2;
if(lineIntersection(l, &line, NULL) == INTERSECTION_SEGMENT_SEGMENT)
return true;
}
return false;
}
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