计算几何习题集

 1 #include <cstdio>
 2 #include <iostream>
 3 #define FOR(i,l,r) for(int i=(l);i<=(r);i++)
 4 #define FE(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
 5 #define rep(i,n) for(int i=0;i<(n);i++)
 6 #define zero(x) ((x>=0?x:-x)<1e-10)
 7 #define debug(x) cout<<#x<<" = "<<x<<endl
 8 using namespace std;
 9 
10 struct pot{
11     double x,y;
12     pot() { x=0; y=0; }
13     pot(double _x, double _y):x(_x),y(_y){};
14 };
15 double cross(pot a,pot b) { return a.x*b.y-a.y*b.x; }
16 pot to_v(pot a,pot b) { pot c=pot(b.x-a.x,b.y-a.y); return c; }
17 pot intersection_line(pot u1,pot u2,pot v1,pot v2)
18 {
19     pot ret = u1;
20     double t = ((u1.x-v1.x)*(v1.y-v2.y) - (u1.y-v1.y)*(v1.x-v2.x))
21              / ((u1.x-u2.x)*(v1.y-v2.y) - (u1.y-u2.y)*(v1.x-v2.x));
22     ret.x += (u2.x-u1.x) * t;
23     ret.y += (u2.y-u1.y) * t;
24     return ret;
25 }
26 
27 pot a[5];
28 int main()
29 {
30     puts("INTERSECTING LINES OUTPUT");
31     int n; scanf("%d",&n);
32     for (pot ans;n--;)
33     {
34         FOR (i,1,4) scanf("%lf%lf",&a[i].x,&a[i].y);
35         if (zero(cross(to_v(a[1],a[2]),to_v(a[3],a[4]))))
36             if (zero(cross(to_v(a[1],a[2]),to_v(a[1],a[3])))) puts("LINE");
37             else puts("NONE");
38         else ans=intersection_line(a[1],a[2],a[3],a[4]),printf("POINT %.2f %.2f\n",ans.x,ans.y);
39     }
40     puts("END OF OUTPUT");
41     return 0;
42 }
43 /*pot intersection_line(pot u1,pot u2,pot v1,pot v2)
44 {
45     pot ret;
46     double a1=u1.y-u2.y,b1=u2.x-u1.x,c1=u1.y*(u1.x-u2.x)-u1.x*(u1.y-u2.y);
47     double a2=v1.y-v2.y,b2=v2.x-v1.x,c2=v1.y*(v1.x-v2.x)-v1.x*(v1.y-v2.y);
48     ret.y=(a1*c2-a2*c1)/(a2*b1-a1*b2);
49     ret.x=(b1*c2-b2*c1)/(a1*b2-a2*b1);
50     return ret;
51 }*/