求相交点
1 /* 2 线段相交模板：判相交、求交点 3 */ 4 #include<stdio.h> 5 #include<string.h> 6 #include<stdlib.h> 7 #include<math.h> 8 9 const double eps = 1e-8; 10 struct Point{ 11 double x,y; 12 }; 13 Point P_ans; 14 double cross( Point a,Point b,Point c ){ 15 return ( b.x-a.x )*( c.y-a.y )-( b.y-a.y )*( c.x-a.x ); 16 } 17 int solve( Point a,Point b,Point c,Point d ){ 18 if( fabs(cross(a,b,c))<=eps&&fabs(cross(a,b,d))<=eps ) 19 return -1;//两条线段在同一条直线上 20 if( fabs((b.x-a.x)*(d.y-c.y)-(b.y-a.y)*(d.x-c.x))<=eps ) 21 return 0;//两条线断平行 22 /* 23 求交点用到叉积(必须保证有交点) 24 交点为p0(x,y) 25 (A-p0)*(B-p0)=0 26 (C-p0)*(D-p0)=0 27 */ 28 double a1,a2,b1,b2,c1,c2; 29 a1 = a.y-b.y,b1 = b.x-a.x,c1 = a.x*b.y-b.x*a.y; 30 a2 = c.y-d.y,b2 = d.x-c.x,c2 = c.x*d.y-d.x*c.y; 31 P_ans.x = (b1*c2-b2*c1)/(a1*b2-a2*b1); 32 P_ans.y = (a2*c1-a1*c2)/(a1*b2-a2*b1); 33 return 1; 34 } 35 int main(){ 36 int n; 37 Point p1,p2,p3,p4; 38 scanf("%d",&n); 39 printf("INTERSECTING LINES OUTPUT "); 40 while( n-- ){ 41 scanf("%lf%lf%lf%lf%lf%lf%lf%lf",&p1.x,&p1.y,&p2.x,&p2.y,&p3.x,&p3.y,&p4.x,&p4.y); 42 int f = solve( p1,p2,p3,p4 ); 43 if( f==-1 ) puts("LINE"); 44 else if( f==0 ) puts("NONE"); 45 else{ 46 printf("POINT %.2lf %.2lf ",P_ans.x,P_ans.y); 47 } 48 } 49 printf("END OF OUTPUT "); 50 return 0; 51 }