HDU1086+几何+判断线段相交

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 1 /*
 2 几何+线段相交
 3 */
 4 #include<stdio.h>
 5 #include<string.h>
 6 #include<stdlib.h>
 7 #include<algorithm>
 8 #include<iostream>
 9 #include<queue>
10 //#include<map>
11 #include<math.h>
12 using namespace std;
13 typedef long long ll;
14 //typedef __int64 int64;
15 const int maxn = 105;
16 const int inf = 0x7fffffff;
17 const double pi=acos(-1.0);
18 const double eps = 1e-8;
19 struct point {
20     double x,y;
21 };
22 struct line{
23     point a,b;
24 };
25 line myline[ maxn ];
26 
27 double xmult( point a,point b,point c ){
28     return ( a.x-c.x )*( b.y-c.y )-( a.y-c.y )*( b.x-c.x );
29 }
30 bool inLine( line now,point p ){
31     double minx,maxx,miny,maxy;
32     minx=min( now.a.x,now.b.x );
33     maxx=max( now.a.x,now.b.x );
34     miny=min( now.a.y,now.b.y );
35     maxy=max( now.a.y,now.b.y );
36     if( p.x>=minx&&p.x<=maxx&&p.y>=miny&&p.y<=maxy )
37         return true;
38     else
39         return false;
40 }
41 bool intersect( line one,line two ){
42     double d1,d2,d3,d4;
43     d1=xmult( two.a,one.b,one.a );
44     d2=xmult( two.b,one.b,one.a );
45     d3=xmult( one.a,two.a,two.b );
46     d4=xmult( one.b,two.a,two.b );
47     if( d1*d2<0&&d3*d4<0 )
48         return true;//相互跨过
49     if( d1==0&&inLine( one,two.a )==true )
50         return true;
51     if( d2==0&&inLine( one,two.b )==true )
52         return true;
53     if( d3==0&&inLine( two,one.a )==true )
54         return true;
55     if( d4==0&&inLine( two,one.b )==true )
56         return true;//分别表示某个点在一条直线上的情况
57     return false;
58 }
59 
60 int main(){
61     int n;
62     while( scanf("%d",&n)!=EOF,n ){
63         for( int i=0;i<n;i++ ){
64             scanf("%lf%lf%lf%lf",&myline[ i ].a.x,&myline[ i ].a.y,&myline[ i ].b.x,&myline[ i ].b.y);
65         }
66         int sum=0;//交点的个数
67         for( int i=0;i<n;i++ ){
68             for( int j=i+1;j<n;j++ ){
69                 if( intersect( myline[ i ],myline[ j ] )==true )
70                     sum++;
71             }
72         }
73         printf("%d\n",sum);
74     }
75     return 0;
76 }

 

posted @ 2013-03-19 18:27  xxx0624  阅读(249)  评论(0)  编辑  收藏  举报