Jip J. Dekker
b5f0d64642
git-subtree-dir: prototype git-subtree-split: 91f7db00d45e7f991b5587ee07f09977ae311ee7
40 lines
974 B
MiniZinc
40 lines
974 B
MiniZinc
% RUNS ON mzn20_fd
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% RUNS ON mzn-fzn_fd
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% RUNS ON mzn20_mip
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% vim: ft=zinc ts=4 sw=4 et
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% Ralph Becket <rafe@csse.unimelb.edu.au>
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% Wed Feb 25 16:43:52 EST 2009
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%
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% Langford's problem (see e.g., http://www.lclark.edu/~miller/langford.html)
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% ------------------
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%
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% Arrange k sets of 1..n such that successive occurrences of any number, k,
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% are separated by k other numbers.
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% There should be 26 solutions to this problem.
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int: k = 2;
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int: n = 7;
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int: nk = n * k;
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array [1..nk] of var 1..n: a; % The sequence.
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array [1..n] of var 1..nk: Fst; % Fst[k] is position of first k.
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% Break some symmetry.
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%
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constraint a[1] <= a[nk];
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% Prune some domains.
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%
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constraint
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forall ( i in 1..n ) ( Fst[i] <= nk - (k - 1) * (i + 1) );
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% The nitty gritty.
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%
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constraint
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forall ( i in 1..n, j in 0..(k - 1) ) ( a[Fst[i] + j * (i + 1)] = i );
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solve :: int_search(Fst, first_fail, indomain_min, complete) satisfy;
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output ["a = ", show(a), ";\n"];
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