Problem 1720. Do the lines intersect?

Created by Ned Gulley

Solve Later

You are given two line segments. Do they cross?

Consider one segment as (x1,y1) to (x2,y2), the other segment as (x3,y3) to (x4,y4). You are given a = [x1 y1; x2 y2]; b = [x3 y3; x4 y4]. Return tf=true if a and b intersect or tf=false if a and b do not touch.

When lines do intersect they will do so cleanly at exactly one non-endpoint. That is, they will not nest, overlap, or "kiss" at the endpoints.

Examples

 a = [0,0; 1,1];
 b = [0,1; 1,0];
 tf = true

 a = [0,0; 1,0];
 b = [0,1; 1,1];
 tf = false

Solve

Solution Stats

Last solution submitted on Aug 20, 2019

Last 200 Solutions

Problem Comments

2 Comments

2 Comments

Celestino on 11 Mar 2014

What about
a = [0,0; 2,2]; b = [1,1; 3,3];
?

Ned Gulley on 12 Mar 2014

Hi Celestino. I added a little bit more clarifying text to the problem statement. That's an interesting test case, but not one I will use for this problem. You could make your own extension to this problem, though!

Solution Comments

Solution 659287

1 Comment

1 Comment

Andrew Newell on 14 May 2017

I like the conceptual clarity of this one.

Solution 416465

1 Comment

1 Comment

Celestino on 11 Mar 2014

For
a = [0,0; 2,2]; b = [1,1; 3,3];
a = [0,0; 2,2]; b = [2,2; 3,3];