You are given two straight line segments, each defined by the coordinates of its endpoints. Segment AB goes from (Ax,Ay) to (Bx,By) and segment CD - from (Cx,Cy) to (Dx,Dy).

How would you determine if the two line segments intersect?

(Assume that you can't just draw the lines and see)

(In reply to re(2): Solution by friedlinguini)

When the fl solution is applied to points that are all colinear, each of the four parenthetical factors is zero, satisfying the equality portion of the <= and therefore reporting an intersection, even if the segments are on disjoint portions of the line they share.

This can be verified using 1,1,2,2,3,3,4,4 as Ax,Ay,Bx,By,Cx,Cy,Dx,Dy or 1,5,2,3,3,1,4,-1.

Posted by Charlie on 2003-07-04 06:02:41