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    why is the example not 7? the 2 nodes in 4 are not connected either?

    • + 0 comments

      same doubt!!

    • + 0 comments

      No pair of red nodes are connected among them. But any yellow node in yellow, if painted in red, will destroy this property, because all of them are connected with at least a red one

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      I think that the two nodes in set 4 are not connected and they should be painted in red not the nodes in set 3.