/* permutation/permutation.c

 * 

 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Brian Gough

 * 

 * 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_permutation.h>

size_t

gsl_permutation_size (const gsl_permutation * p)

{

  return p->size ;

}

size_t *

gsl_permutation_data (const gsl_permutation * p)

{

  return p->data ;

}

int

gsl_permutation_swap (gsl_permutation * p, const size_t i, const size_t j)

{

  const size_t size = p->size ;

  if (i >= size)

    {

      GSL_ERROR("first index is out of range", GSL_EINVAL);

    }

  if (j >= size)

    {

      GSL_ERROR("second index is out of range", GSL_EINVAL);

    }

  if (i != j)

    {

      size_t tmp = p->data[i];

      p->data[i] = p->data[j];

      p->data[j] = tmp;

    }

  return GSL_SUCCESS;

}

int

gsl_permutation_valid (const gsl_permutation * p)

{

  const size_t size = p->size ;

  size_t i, j ;

  for (i = 0; i < size; i++) 

    {

      if (p->data[i] >= size)

        {

          GSL_ERROR("permutation index outside range", GSL_FAILURE) ;

        }

      for (j = 0; j < i; j++)

        {

          if (p->data[i] == p->data[j])

            {

              GSL_ERROR("duplicate permutation index", GSL_FAILURE) ;

            }

        }

    }

  return GSL_SUCCESS;

}

void

gsl_permutation_reverse (gsl_permutation * p)

{

  const size_t size = p->size ;

  size_t i ;

  for (i = 0; i < (size / 2); i++) 

    {

      size_t j = size - i - 1;

      size_t tmp = p->data[i] ;

      p->data[i] = p->data[j] ;

      p->data[j] = tmp ;

    }

}

int 

gsl_permutation_inverse (gsl_permutation * inv, const gsl_permutation * p)

{

  const size_t size = p->size ;

  size_t i ;

  if (inv->size != size)

    {

      GSL_ERROR("permutation lengths are not equal", GSL_EBADLEN);

    }

  for (i = 0; i < size; i++) 

    {

      inv->data[p->data[i]] = i ;

    }

  return GSL_SUCCESS ;

}

int

gsl_permutation_next (gsl_permutation * p)

{

  /* Replaces p with the next permutation (in the standard lexicographical

   * ordering).  Returns GSL_FAILURE if there is no next permutation.

   */

  const size_t size = p->size;

  size_t i, j, k;

  if (size < 2)

    {

      return GSL_FAILURE;

    }

  i = size - 2;

  while ((p->data[i] > p->data[i+1]) && (i != 0))

    {

      i--;

    }

  if ((i == 0) && (p->data[0] > p->data[1]))

    {

     return GSL_FAILURE;

    }

  k = i + 1;

  for (j = i + 2; j < size; j++ )

    {

      if ((p->data[j] > p->data[i]) && (p->data[j] < p->data[k]))

        {

          k = j;

        }

    }

  /* swap i and k */

  {

    size_t tmp = p->data[i];

    p->data[i] = p->data[k];

    p->data[k] = tmp;

  }

  for (j = i + 1; j <= ((size + i) / 2); j++)

    {

      size_t tmp = p->data[j];

      p->data[j] = p->data[size + i - j];

      p->data[size + i - j] = tmp;

    }

  return GSL_SUCCESS;

}

int

gsl_permutation_prev (gsl_permutation * p)

{

  const size_t size = p->size;

  size_t i, j, k;

  if (size < 2)

    {

      return GSL_FAILURE;

    }

  i = size - 2;

  while ((p->data[i] < p->data[i+1]) && (i != 0))

    {

      i--;

    }

  if ((i == 0) && (p->data[0] < p->data[1]))

    {

      return GSL_FAILURE;

    }

  k = i + 1;

  for (j = i + 2; j < size; j++ )

    {

      if ((p->data[j] < p->data[i]) && (p->data[j] > p->data[k]))

        {

          k = j;

        }

    }

  /* swap i and k */

  {

    size_t tmp = p->data[i];

    p->data[i] = p->data[k];

    p->data[k] = tmp;

  }

  for (j = i + 1; j <= ((size + i) / 2); j++)

    {

      size_t tmp = p->data[j];

      p->data[j] = p->data[size + i - j];

      p->data[size + i - j] = tmp;

    }

  return GSL_SUCCESS;

}

int

gsl_permutation_mul (gsl_permutation * p, const gsl_permutation * pa, const gsl_permutation * pb)

{

  size_t i;

  const size_t size = p->size;

  if (pa->size != size)

    {

      GSL_ERROR("size of result does not match size of pa", GSL_EINVAL);

    }

  if (pb->size != size)

    {

      GSL_ERROR("size of result does not match size of pb", GSL_EINVAL);

    }

  for (i = 0; i < size; i++)

    {

      p->data[i] = pb->data[pa->data[i]];

    }

  return GSL_SUCCESS;

}

int

gsl_permutation_memcpy (gsl_permutation * dest,

                        const gsl_permutation * src)

{

  const size_t src_size = src->size;

  const size_t dest_size = dest->size;

  if (src_size != dest_size)

    {

      GSL_ERROR ("permutation lengths are not equal", GSL_EBADLEN);

    }

  {

    size_t j;

    for (j = 0; j < src_size; j++)

      {

        dest->data[j] = src->data[j];

      }

  }

  return GSL_SUCCESS;

}