## Copyright (C) 2001 Paul Kienzle
##
## This file is part of Octave.
##
## Octave 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 2, or (at your option)
## any later version.
##
## Octave 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 Octave; see the file COPYING. If not, write to the Free
## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
## 02110-1301, USA.
## -*- texinfo -*-
## @deftypefn {Function File} {} perms (@var{v})
##
## Generate all permutations of @var{v}, one row per permutation. The
## result has size @code{factorial (@var{n}) * @var{n}}, where @var{n}
## is the length of @var{v}.
##
## @end deftypefn
function A = perms (v)
v = v(:);
n = length (v);
if (n == 1)
A = v;
else
B = perms (v(1:n-1));
Bidx = 1:size (B, 1);
A = v(n) * ones (prod (2:n), n);
A(Bidx,1:n-1) = B;
k = size (B, 1);
for x = n-1:-1:2
A(k+Bidx,1:x-1) = B(Bidx,1:x-1);
A(k+Bidx,x+1:n) = B(Bidx,x:n-1);
k = k + size (B, 1);
endfor
A(k+Bidx,2:n) = B;
endif
endfunction
/*
@GROUP
specfun
@SYNTAX
perms([2,7,4])
@DOC
.
@EXAMPLES
.
@NOTES
.
@SEE
**/