OJ-Problems-Source/HDOJ/1632_autoAC.cpp

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#include<stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
using namespace std;
#define N 155
#define eps 1e-8
struct TPoint
{
double x,y;
}s;
struct TPolygon
{
int n;
TPoint p[N];
}ply1,ply2,ans;
double maxdist;
int dblcmp(double a) {return a<-eps?-1:a>eps?1:0;}
double MAX(double a,double b) {return a>b?a:b;}
double cross(TPoint a,TPoint b,TPoint c)
{
return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
}
double plyarea(TPolygon res)
{
int i;
double area=0;
res.p[res.n]=res.p[0];
for(i=0;i<res.n;i++)
area+=cross(s,res.p[i],res.p[i+1]);
return area;
}
TPolygon cut(TPolygon res,TPoint s,TPoint e)
{
int d1,d2,i,t;
double s1,s2;
TPoint a;
TPolygon b;
b.n=0;
res.p[res.n]=res.p[0];
for(i=0,t=0;i<res.n;i++)
{
d1=dblcmp(s1=cross(res.p[i],s,e));
d2=dblcmp(s2=cross(res.p[i+1],s,e));
if(d1>=0) b.p[t++]=res.p[i];
if(d1*d2<0)
{
a.x=(s2*res.p[i].x-s1*res.p[i+1].x)/(s2-s1);
a.y=(s2*res.p[i].y-s1*res.p[i+1].y)/(s2-s1);
b.p[t++]=a;
}
}
b.n=t;
return b;
}
int main()
{
while(scanf("%d",&ply1.n),ply1.n)
{
int i;
double sumarea,area;
for(i=0;i<ply1.n;i++) scanf("%lf%lf",&ply1.p[i].x,&ply1.p[i].y);
s.x=0; s.y=0;
if((dblcmp(sumarea=plyarea(ply1)))<0) reverse(ply1.p,ply1.p+ply1.n);
ply1.p[ply1.n]=ply1.p[0];
sumarea=fabs(sumarea);
scanf("%d",&ply2.n);
for(i=0;i<ply2.n;i++) scanf("%lf%lf",&ply2.p[i].x,&ply2.p[i].y);
if((dblcmp(area=plyarea(ply2)))<0) reverse(ply2.p,ply2.p+ply2.n);
sumarea+=fabs(area);
ply2.p[ply2.n]=ply2.p[0];
ans=ply1;
for(i=0;i<ply2.n;i++)
ans=cut(ans,ply2.p[i],ply2.p[i+1]);
area=fabs(plyarea(ans));
printf("%8.2lf",sumarea/2-area);
}
puts("");
return 0;
}