LA_library/permutation.h
2009-11-12 21:01:19 +00:00

32 lines
1.1 KiB
C++

/*
LA: linear algebra C++ interface library
Copyright (C) 2008 Jiri Pittner <jiri.pittner@jh-inst.cas.cz> or <jiri@pittnerovi.com>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef _PERMUTATION_H
#define _PERMUTATION_H
namespace LA {
template<typename T>
const NRVec<T> inversepermutation(const NRVec<T> &p, const T offset=0)
{
int n=p.size();
NRVec<T> q(n);
if(!offset) for(int i=0; i<n; ++i) q[p[i]]=i;
else for(int i=0; i<n; ++i) q[p[i]-offset]=i+offset;
return q;
}
}//namespace
#endif