46 lines
1.2 KiB
C++
46 lines
1.2 KiB
C++
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/*
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* This file is part of Codecrypt.
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*
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* Codecrypt is free software: you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or (at
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* your option) any later version.
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*
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* Codecrypt is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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* License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with Codecrypt. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "permutation.h"
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#include "prng.h"
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#include "matrix.h"
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void permutation::compute_inversion (permutation&r) const
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{
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r.resize (size(), 0);
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for (uint i = 0; i < size(); ++i)
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r[item (i) ] = i;
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}
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void permutation::generate_random (uint size, prng&rng)
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{
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resize (size, 0);
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uint i;
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for (i = 0; i < size; ++i) item (i) = i;
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//knuth shuffle
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for (i = size - 1; i > 0; --i) {
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uint j = rng.random (i + 1);
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if (i != j) {
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uint t = item (i);
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item (i) = item (j);
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item (j) = t;
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}
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}
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}
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