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/* combination/combination.c
* based on permutation/permutation.c by Brian Gough
*
* Copyright (C) 2001 Szymon Jaroszewicz
*
* 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, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include <config.h>
#include <gsl/gsl_errno.h>
#include <gsl/gsl_combination.h>
size_t
gsl_combination_n (const gsl_combination * c)
{
return c->n ;
}
size_t
gsl_combination_k (const gsl_combination * c)
{
return c->k ;
}
size_t *
gsl_combination_data (const gsl_combination * c)
{
return c->data ;
}
int
gsl_combination_valid (gsl_combination * c)
{
const size_t n = c->n ;
const size_t k = c->k ;
size_t i, j ;
if( k > n )
{
GSL_ERROR("combination has k greater than n", GSL_FAILURE) ;
}
for (i = 0; i < k; i++)
{
const size_t ci = c->data[i];
if (ci >= n)
{
GSL_ERROR("combination index outside range", GSL_FAILURE) ;
}
for (j = 0; j < i; j++)
{
if (c->data[j] == ci)
{
GSL_ERROR("duplicate combination index", GSL_FAILURE) ;
}
if (c->data[j] > ci)
{
GSL_ERROR("combination indices not in increasing order",
GSL_FAILURE) ;
}
}
}
return GSL_SUCCESS;
}
int
gsl_combination_next (gsl_combination * c)
{
/* Replaces c with the next combination (in the standard lexicographical
* ordering). Returns GSL_FAILURE if there is no next combination.
*/
const size_t n = c->n;
const size_t k = c->k;
size_t *data = c->data;
size_t i;
if(k == 0)
{
return GSL_FAILURE;
}
i = k - 1;
while(i > 0 && data[i] == n - k + i)
{
i--;
}
if(i == 0 && data[i] == n - k)
{
return GSL_FAILURE;
}
data[i]++;
for(; i < k - 1; i++)
{
data[i + 1] = data[i] + 1;
}
return GSL_SUCCESS;
}
int
gsl_combination_prev (gsl_combination * c)
{
/* Replaces c with the previous combination (in the standard
* lexicographical ordering). Returns GSL_FAILURE if there is no
* previous combination.
*/
const size_t n = c->n;
const size_t k = c->k;
size_t *data = c->data;
size_t i;
if(k == 0)
{
return GSL_FAILURE;
}
i = k - 1;
while(i > 0 && data[i] == data[i-1] + 1)
{
i--;
}
if(i == 0 && data[i] == 0)
{
return GSL_FAILURE;
}
data[i++]--;
for(; i < k; i++)
{
data[i] = n - k + i;
}
return GSL_SUCCESS;
}
int
gsl_combination_memcpy (gsl_combination * dest, const gsl_combination * src)
{
const size_t src_n = src->n;
const size_t src_k = src->k;
const size_t dest_n = dest->n;
const size_t dest_k = dest->k;
if (src_n != dest_n || src_k != dest_k)
{
GSL_ERROR ("combination lengths are not equal", GSL_EBADLEN);
}
{
size_t j;
for (j = 0; j < src_k; j++)
{
dest->data[j] = src->data[j];
}
}
return GSL_SUCCESS;
}
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