Interval Scheduling Confusion I am reading some notes about interval scheduling. I gives the following diagram:


and states that:

r2 is compatible with r3, while r2 and r1 are conflicting. Similarly, the set {r1, r3, r4} is compatible, while {r2, r3, r4} is not compatible.

I can understand that set (r1, r3, r4) is compatible. How (r2, r3, r4) are not compatible. Since they are not overlapping, isn't they are compatible?
That looks like an error in your notes.  {r2,r3,r4} are compatible.