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   DIR Return to: general Hamiltonian cycles problem
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       #Post#: 16--------------------------------------------------
       border-reorder
       By: gsgs Date: June 22, 2023, 5:50 am
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       my vertex-reordering program :
  HTML http://magictour.free.fr/reorder.c
       most Hamiltonian cycle program in most cases benefit from an
       initial
       reordering of the vertices for small border-size.
       See also the Pettersson-2014-paper.
       find a permutation P such that
       max {B({P(1),...,P(k)} , k=1,..,n} is low
       or sum {B(P,k) , k=1,..,n} is low
       or max (B({P(1),...,P(k)}+B({P{k+1),...,P(n)}),k=1..n} is low
       J_k:={1,2,..,k}
       G=(V,E)=(J_n,E), n=#V ,
       S_n = {P:J_n c->> J_n ,P bijective} permutations
       B(S) = {v in V , exists u in S with (u,v) in E} , for S<=V
       B(P,k)=B(P(1),..,P(k))
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