Given a matrix of ones and zeros, you must determine if there are any doughnuts present (would Homer Simpson like it?). A doughnut is a 4-connected region of ones completely enclosing a 4-connected region of zeros. You can assume that any regions of ones are either blobs (or genus 0) or doughnuts (genus 1). Thus if you find any hole in a region of ones, it is a doughnut. Also, there are no nested doughnuts.
Return true if any doughnuts are present, otherwise false.
Examples:
This is a doughnut:
1 1 1
1 0 1
1 1 1
Here is another doughnut:
0 0 0 1 1 1
0 1 1 1 0 1
0 0 1 0 0 1
0 0 1 1 1 1
This is not a doughnut:
0 1 0
1 0 1
0 1 0
because the ones are not 4-connected and so can't surround anything.
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mmm... the image processing toolbox seems to be available again?
Oh! Thanks for pointing that out. It will disappear again shortly. Sorry about that.
Sounds good (it was too easy this way)
Okay, we should be back to no-toolbox coding.