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- /* permutation/permutation.c
- *
- * Copyright (C) 2001, 2002 Nicolas Darnis
- *
- * 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.
- */
- /* Modified for GSL by Brian Gough.
- * Use in-place algorithms, no need for workspace
- * Use conventions for canonical form given in Knuth (opposite of Sedgewick)
- */
- #include "gsl__config.h"
- #include "gsl_errno.h"
- #include "gsl_permutation.h"
- int
- gsl_permutation_linear_to_canonical (gsl_permutation * q,
- const gsl_permutation * p)
- {
- const size_t n = p->size;
- size_t i, k, s;
- size_t t = n;
- const size_t *const pp = p->data;
- size_t *const qq = q->data;
- if (q->size != p->size)
- {
- GSL_ERROR ("size of q does not match size of p", GSL_EINVAL);
- }
- for (i = 0; i < n; i++)
- {
- k = pp[i];
- s = 1;
- while (k > i)
- {
- k = pp[k];
- s++;
- }
- if (k < i)
- continue;
- /* Now have k == i, i.e the least in its cycle, and s == cycle length */
- t -= s;
- qq[t] = i;
- k = pp[i];
- s = 1;
- while (k > i)
- {
- qq[t + s] = k;
- k = pp[k];
- s++;
- }
- if (t == 0)
- break;
- }
- return GSL_SUCCESS;
- }
- int
- gsl_permutation_canonical_to_linear (gsl_permutation * p,
- const gsl_permutation * q)
- {
- size_t i, k, kk, first;
- const size_t n = p->size;
- size_t *const pp = p->data;
- const size_t *const qq = q->data;
- if (q->size != p->size)
- {
- GSL_ERROR ("size of q does not match size of p", GSL_EINVAL);
- }
- for (i = 0; i < n; i++)
- {
- pp[i] = i;
- }
- k = qq[0];
- first = pp[k];
- for (i = 1; i < n; i++)
- {
- kk = qq[i];
- if (kk > first)
- {
- pp[k] = pp[kk];
- k = kk;
- }
- else
- {
- pp[k] = first;
- k = kk;
- first = pp[kk];
- }
- }
- pp[k] = first;
- return GSL_SUCCESS;
- }
- size_t
- gsl_permutation_inversions (const gsl_permutation * p)
- {
- size_t count = 0;
- size_t i, j;
- const size_t size = p->size;
- for (i = 0; i < size - 1; i++)
- {
- for (j = i + 1; j < size; j++)
- {
- if (p->data[i] > p->data[j])
- {
- count++;
- }
- }
- }
- return count;
- }
- size_t
- gsl_permutation_linear_cycles (const gsl_permutation * p)
- {
- size_t i, k;
- size_t count = 0;
- const size_t size = p->size;
- for (i = 0; i < size; i++)
- {
- k = p->data[i];
- while (k > i)
- {
- k = p->data[k];
- }
- if (k < i)
- continue;
- count++;
- }
- return count;
- }
- size_t
- gsl_permutation_canonical_cycles (const gsl_permutation * p)
- {
- size_t i;
- size_t count = 1;
- size_t min = p->data[0];
- for (i = 0; i < p->size; i++)
- {
- if (p->data[i] < min)
- {
- min = p->data[i];
- count++;
- }
- }
- return count;
- }
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