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