Mercurial > octave-nkf
view scripts/specfun/perms.m @ 5915:b2e1be30c8e9 ss-2-9-7
[project @ 2006-07-28 18:08:56 by jwe]
author | jwe |
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date | Fri, 28 Jul 2006 18:08:56 +0000 |
parents | 1fe78adb91bc |
children | 3f3e86e9fb57 |
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## 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 i = n-1:-1:2 A(k+Bidx,1:i-1) = B(Bidx,1:i-1); A(k+Bidx,i+1:n) = B(Bidx,i:n-1); k = k + size (B, 1); endfor A(k+Bidx,2:n) = B; endif endfunction