Mercurial > forge
comparison main/specfun/perms.m @ 0:6b33357c7561 octave-forge
Initial revision
| author | pkienzle |
|---|---|
| date | Wed, 10 Oct 2001 19:54:49 +0000 |
| parents | |
| children | b3cb3d604550 |
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| -1:000000000000 | 0:6b33357c7561 |
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| 1 ## Copyright (C) 2001 Paul Kienzle | |
| 2 ## | |
| 3 ## This program is free software; you can redistribute it and/or modify | |
| 4 ## it under the terms of the GNU General Public License as published by | |
| 5 ## the Free Software Foundation; either version 2 of the License, or | |
| 6 ## (at your option) any later version. | |
| 7 ## | |
| 8 ## This program is distributed in the hope that it will be useful, | |
| 9 ## but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 10 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 11 ## GNU General Public License for more details. | |
| 12 ## | |
| 13 ## You should have received a copy of the GNU General Public License | |
| 14 ## along with this program; if not, write to the Free Software | |
| 15 ## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
| 16 | |
| 17 ## A = perms(v) | |
| 18 ## generate all permutations of v, one row per permutation. | |
| 19 ## The resulting A has size n! x n, where n is the length of v | |
| 20 ## so keep v small! | |
| 21 function A = perms(v) | |
| 22 n = length(v); | |
| 23 if (n == 1) | |
| 24 A = v; | |
| 25 else | |
| 26 B = perms(v(1:n-1)); | |
| 27 Bidx = 1:size(B,1); | |
| 28 A = v(n) * ones(prod(2:n), n); | |
| 29 A (Bidx, 1:n-1) = B; | |
| 30 k = size(B,1); | |
| 31 for i = n-1:-1:2 | |
| 32 A (k+Bidx, 1:i-1) = B(Bidx, 1:i-1); | |
| 33 A (k+Bidx, i+1:n) = B(Bidx, i:n-1); | |
| 34 k = k + size(B,1); | |
| 35 end | |
| 36 A (k+Bidx, 2:n) = B; | |
| 37 endif | |
| 38 endfunction |