17 lines
769 B
MiniZinc
17 lines
769 B
MiniZinc
include "tree.mzn";
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include "subgraph.mzn";
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predicate fzn_path(array[int] of $$N: from, array[int] of $$N: to,
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var $$N: s, var $$N: t, array[$$N] of var bool: ns, array[int] of var bool: es) =
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let { int: E = length(es);
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array[1..2*E] of int: dfrom = from ++ to;
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array[1..2*E] of int: dto = to ++ from;
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array[1..2*E] of var bool: des;
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} in
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/* ensure that the directed edges selected agree with undirected edges */
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forall(e in 1..E)(es[e-1+min(index_set(es))] <-> (des[e] \/ des[e+E])) /\
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/* duplicate the edges so that the we can use directed graph path */
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fzn_dpath(dfrom,dto,s,t,ns,des);
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%-----------------------------------------------------------------------------%
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