Thanks for crafting such interesting family of graph Katas. I wish OP returned and continued. Also it will be more interesting to see Graph problems applied for more real world situations and without mentioning Graph itself.

@eberfinn what if you could get list of simple dividers first?

Great Kata, thanks! Please more Graph Katas :)

Any follow up Katas with bridge between first and last islands?

Very interesting Kata, but like many already mentioned lack of proper Test cases makes it useless. It would be great to have test case like that: H?!el,lo World!

Sort is overkill here. IMO too much upvotes.

If you already have all magic chars inside map please use it instead of specifying magic chars second time in if statement