path connected algorithm to determine number of domains

I need an algorithm to determine how many domains I have. I have 4 sides that always touch, 3 are fixed and I am varying 1 of them. 2 sides are straight lines and the other 2 are large waves which when all 4 connected, form 1 domain. The problem is, sometimes my program changes this one side such that 1) it crosses over itself making more than 1 domain and 2) sometimes its amplitude is large enough it intersects another side.

I have been suggested to check path connectedness. Does anyone know if an algorithm has been posted for this?

or

Does anyone know of a better algorithm?

[Alex]

sorry about that, it wasn't let me posting so I was changing things until I figured out what was wrong