2014
03-01

# Area2

(3<= n，m <= 500)

(3<= n，m <= 500)

4 4
0 0
0 1
1 1
1 0
0.5 0.5
0.5 1.5
1.5 1.5
1.5 0.5

1.75

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<math.h>
#include<algorithm>
const int maxn = 555;
const int maxisn = 10;
const double eps = 1e-8;
const double pi = acos(-1.0);
int dcmp(double x)
{
if(x > eps) return 1;
return x < -eps ? -1 : 0;
}
inline double min(double a, double b)
{return a < b ? a : b;}
inline double max(double a, double b)
{return a > b ? a : b;}
inline double Sqr(double x)
{return x * x;}
struct Point
{
double x, y;
Point(){x = y = 0;}
Point(double a, double b)
{x = a, y = b;}
inline Point operator-(const Point &b)const
{return Point(x - b.x, y - b.y);}
inline Point operator+(const Point &b)const
{return Point(x + b.x, y + b.y);}
inline double dot(const Point &b)const
{return x * b.x + y * b.y;}
inline double cross(const Point &b, const Point &c)const
{return (b.x - x) * (c.y - y) - (c.x - x) * (b.y - y);}
};
Point LineCross(const Point &a, const Point &b, const Point &c, const Point &d)
{
double u = a.cross(b, c), v = b.cross(a, d);
return Point((c.x * v + d.x * u) / (u + v), (c.y * v + d.y * u) / (u + v));
}
double PolygonArea(Point p[], int n)
{
if(n < 3) return 0.0;
double s = p[0].y * (p[n - 1].x - p[1].x);
p[n] = p[0];
for(int i = 1; i < n; ++ i)
s += p[i].y * (p[i - 1].x - p[i + 1].x);
return fabs(s * 0.5);
}
double CPIA(Point a[], Point b[], int na, int nb)//ConvexPolygonIntersectArea
{
Point p[maxisn], tmp[maxisn];
int i, j, tn, sflag, eflag;
a[na] = a[0], b[nb] = b[0];
memcpy(p, b, sizeof(Point) * (nb + 1));
for(i = 0; i < na && nb > 2; ++ i)
{
sflag = dcmp(a[i].cross(a[i + 1], p[0]));
for(j = tn = 0; j < nb; ++ j, sflag = eflag)
{
if(sflag >= 0) tmp[tn ++] = p[j];
eflag = dcmp(a[i].cross(a[i + 1], p[j + 1]));
if((sflag ^ eflag) == -2)
tmp[tn ++] = LineCross(a[i], a[i + 1], p[j], p[j + 1]);
}
memcpy(p, tmp, sizeof(Point) * tn);
nb = tn, p[nb] = p[0];
}
if(nb < 3) return 0.0;
return PolygonArea(p, nb);
}
double SPIA(Point a[], Point b[], int na, int nb)//SimplePolygonIntersectArea
{
int i, j;
Point t1[4], t2[4];
double res = 0, if_clock_t1, if_clock_t2;
a[na] = t1[0] = a[0], b[nb] = t2[0] = b[0];
for(i = 2; i < na; ++ i)
{
t1[1] = a[i - 1], t1[2] = a[i];
if_clock_t1 = dcmp(t1[0].cross(t1[1], t1[2]));
if(if_clock_t1 < 0) std::swap(t1[1], t1[2]);
for(j = 2; j < nb; ++ j)
{
t2[1] = b[j - 1], t2[2] = b[j];
if_clock_t2 = dcmp(t2[0].cross(t2[1], t2[2]));
if(if_clock_t2 < 0) std::swap(t2[1], t2[2]);
res += CPIA(t1, t2, 3, 3) * if_clock_t1 * if_clock_t2;
}
}
return PolygonArea(a, na) + PolygonArea(b, nb) - res;
}
Point p1[maxn], p2[maxn];
int n1, n2;
int main()
{
int i;
while(scanf("%d%d", &n1, &n2) != EOF)
{
for(i = 0; i < n1; ++ i) scanf("%lf%lf", &p1[i].x, &p1[i].y);
for(i = 0; i < n2; ++ i) scanf("%lf%lf", &p2[i].x, &p2[i].y);
printf("%.2f\n", SPIA(p1, p2, n1, n2) + eps);
}
return 0;
}