/usr/include/getfem/bgeot_permutations.h is in libgetfem++-dev 4.2.1~beta1~svn4635~dfsg-3+b1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 | /* -*- c++ -*- (enables emacs c++ mode) */
/*===========================================================================
Copyright (C) 2004-2012 Julien Pommier
This file is a part of GETFEM++
Getfem++ is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version along with the GCC Runtime Library
Exception either version 3.1 or (at your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License and GCC Runtime Library Exception for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
As a special exception, you may use this file as it is a part of a free
software library without restriction. Specifically, if other files
instantiate templates or use macros or inline functions from this file,
or you compile this file and link it with other files to produce an
executable, this file does not by itself cause the resulting executable
to be covered by the GNU Lesser General Public License. This exception
does not however invalidate any other reasons why the executable file
might be covered by the GNU Lesser General Public License.
===========================================================================*/
#include <vector>
#include "bgeot_config.h"
namespace bgeot {
/**
generation of permutations, and ranking/unranking of these.
based on algorithms detailed in "Ranking and Unranking Permutations in linear time", W. Myrvold, F. Ruskey
( http://www.csr.uvic.ca/~fruskey/Publications/RankPerm.html )
note that this is not lexigraphical order, and to_rank(0) != {0,1,2,3,...} (it is {1,2,3,...,n,0})
however, the reset(), finished(), and ++ operator are based on the lexicagraphical ordering
*/
class permutation : public std::vector<dim_type> {
size_type remaining;
public:
permutation(size_type n) : std::vector<dim_type>(n) { reset(); }
size_type nb_permutations() { return permutation::nb_permutations(size()); }
static size_type nb_permutations(size_type n)
{ size_type f=1; for (; n>1; --n) f *= n; return f; }
void reset() {
remaining = 1;
for (size_type i=0; i < size(); ++i)
{ (*this)[i] = dim_type(i); remaining *= (i+1); }
}
permutation& to_rank(size_type r);
permutation inversed() const {
permutation pinv(*this);
for (size_type i=0; i < size(); ++i) pinv[(*this)[i]] = dim_type(i);
return pinv;
}
size_type rank() const;
bool finished() const { return remaining == 0; }
/* increment in lexicographical order (not the best, but it is simple) */
const permutation &operator ++();
template < typename CONT1, typename CONT2 > void apply_to(const CONT1& src, CONT2& dest)
{ for (size_type i=0; i < size(); ++i) dest[i] = src[(*this)[i]]; }
};
inline permutation& permutation::to_rank(size_type r) {
reset();
for (size_type n = size(); n; --n) {
std::swap((*this)[n-1], (*this)[r % n]);
r /= n;
}
return (*this);
}
inline size_type permutation::rank() const {
permutation p(*this);
permutation pinv(p.inversed());
size_type mul=1, r=0;
for (size_type n=size(); n>1; --n) {
dim_type s = p[n-1];
std::swap(p[n-1], p[pinv[n-1]]);
std::swap(pinv[s],pinv[n-1]);
r += s*mul; mul*=n;
}
return r;
}
inline const permutation &permutation::operator ++() {
if (--remaining == 0) return (*this);
size_type i = size()-2, j=size()-1;
while ((*this)[i] > (*this)[i+1]) i--;
while ((*this)[i] > (*this)[j]) j--;
std::swap((*this)[i], (*this)[j]);
for (size_type r = size()-1, s=i+1; r>s; --r, ++s) std::swap((*this)[r],(*this)[s]);
return (*this);
}
}
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