complement/3

Simple two-step algorithm. You could be smarter, I suppose.%.

complement(+ Graph, - NewGraph)*

Unify NewGraph with the graph complementary to Graph. In the next example:


 ?- complement([1-[3,5],2-[4],3-[],
 4-[1,2,7,5],5-[],6-[],7-[],8-[]], NL).

 NL = [1-[2,4,6,7,8],2-[1,3,5,6,7,8],3-[1,2,4,5,6,7,8],
 4-[3,5,6,8],5-[1,2,3,4,6,7,8],6-[1,2,3,4,5,7,8],
 7-[1,2,3,4,5,6,8],8-[1,2,3,4,5,6,7]]