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