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/* combination/combination.c
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* based on permutation/permutation.c by Brian Gough
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*
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* Copyright (C) 2001 Szymon Jaroszewicz
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#include <config.h>
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#include <gsl/gsl_errno.h>
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#include <gsl/gsl_combination.h>
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size_t
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gsl_combination_n (const gsl_combination * c)
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{
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return c->n ;
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}
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size_t
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gsl_combination_k (const gsl_combination * c)
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{
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return c->k ;
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}
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size_t *
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gsl_combination_data (const gsl_combination * c)
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{
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return c->data ;
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}
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int
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gsl_combination_valid (gsl_combination * c)
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{
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const size_t n = c->n ;
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const size_t k = c->k ;
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size_t i, j ;
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if( k > n )
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{
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GSL_ERROR("combination has k greater than n", GSL_FAILURE) ;
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}
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for (i = 0; i < k; i++)
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{
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const size_t ci = c->data[i];
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if (ci >= n)
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{
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GSL_ERROR("combination index outside range", GSL_FAILURE) ;
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}
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for (j = 0; j < i; j++)
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{
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if (c->data[j] == ci)
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{
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GSL_ERROR("duplicate combination index", GSL_FAILURE) ;
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}
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if (c->data[j] > ci)
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{
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GSL_ERROR("combination indices not in increasing order",
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GSL_FAILURE) ;
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}
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}
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}
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return GSL_SUCCESS;
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}
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int
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gsl_combination_next (gsl_combination * c)
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{
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/* Replaces c with the next combination (in the standard lexicographical
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* ordering). Returns GSL_FAILURE if there is no next combination.
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*/
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const size_t n = c->n;
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const size_t k = c->k;
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size_t *data = c->data;
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size_t i;
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if(k == 0)
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{
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return GSL_FAILURE;
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}
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i = k - 1;
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while(i > 0 && data[i] == n - k + i)
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{
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i--;
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}
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if(i == 0 && data[i] == n - k)
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{
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return GSL_FAILURE;
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}
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data[i]++;
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for(; i < k - 1; i++)
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{
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data[i + 1] = data[i] + 1;
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}
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return GSL_SUCCESS;
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}
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int
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gsl_combination_prev (gsl_combination * c)
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{
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/* Replaces c with the previous combination (in the standard
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* lexicographical ordering). Returns GSL_FAILURE if there is no
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* previous combination.
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*/
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const size_t n = c->n;
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const size_t k = c->k;
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size_t *data = c->data;
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size_t i;
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if(k == 0)
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{
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return GSL_FAILURE;
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}
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i = k - 1;
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while(i > 0 && data[i] == data[i-1] + 1)
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{
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i--;
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}
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if(i == 0 && data[i] == 0)
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{
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return GSL_FAILURE;
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}
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data[i++]--;
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for(; i < k; i++)
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{
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data[i] = n - k + i;
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}
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return GSL_SUCCESS;
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}
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int
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gsl_combination_memcpy (gsl_combination * dest, const gsl_combination * src)
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{
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const size_t src_n = src->n;
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const size_t src_k = src->k;
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const size_t dest_n = dest->n;
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const size_t dest_k = dest->k;
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if (src_n != dest_n || src_k != dest_k)
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{
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GSL_ERROR ("combination lengths are not equal", GSL_EBADLEN);
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}
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{
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size_t j;
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for (j = 0; j < src_k; j++)
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{
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dest->data[j] = src->data[j];
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}
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}
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return GSL_SUCCESS;
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}
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