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dekker.one
1include "tree.mzn";
2include "subgraph.mzn";
3
4predicate fzn_path(array[int] of $$N: from, array[int] of $$N: to,
5 var $$N: s, var $$N: t, array[$$N] of var bool: ns, array[int] of var bool: es) =
6 let { int: E = length(es);
7 array[1..2*E] of int: dfrom = from ++ to;
8 array[1..2*E] of int: dto = to ++ from;
9 array[1..2*E] of var bool: des;
10 } in
11 /* ensure that the directed edges selected agree with undirected edges */
12 forall(e in 1..E)(es[e-1+min(index_set(es))] <-> (des[e] \/ des[e+E])) /\
13 /* duplicate the edges so that the we can use directed graph path */
14 fzn_dpath(dfrom,dto,s,t,ns,des);
15
16%-----------------------------------------------------------------------------%