Impossible Bridge Build Rule

[erthium]

For the solver, general rules are applied and working. I'm not exactly sure if it's necessary, but there could be one more rule added to increase the speed and accuracy.

Also it's important that the solver works as much human as possible, so that the iteration count can show the similar difficulty for humans.

Here is the suggested rule:

And island that has count of 2, cannot send double bridge to another island that has count of 2.
And island that has count of 1, cannot send any bridge to another island that has count of 1.