81 lines
2.0 KiB
C
81 lines
2.0 KiB
C
/* -*-comment-start: "//";comment-end:""-*-
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* GNU Mes --- Maxwell Equations of Software
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* Copyright © 2017,2018 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
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* Copyright © 2021 Paul Dersey <pdersey@gmail.com>
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*
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* This file is part of GNU Mes.
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*
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* GNU Mes is free software; you can redistribute it and/or modify it
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* 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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* GNU Mes 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
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* GNU 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 GNU Mes. If not, see <http://www.gnu.org/licenses/>.
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*/
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/* See: https://en.wikipedia.org/wiki/Quicksort */
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#include <stdlib.h>
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static void
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qswap (char *a, char *b, size_t size)
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{
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while (size-- > 0)
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{
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char tmp = *a;
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*a++ = *b;
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*b++ = tmp;
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}
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}
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static size_t
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qpart (char *base, size_t lo, size_t hi, size_t size,
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int (*compare) (void const *, void const *))
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{
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char *pivot = base + hi * size;
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size_t i = lo;
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for (size_t j = lo; j < hi; j++)
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{
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char *pj = base + j * size;
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if (pj != pivot && compare (pj, pivot) < 0)
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{
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void *pi = base + i * size;
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qswap (pi, pj, size);
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i++;
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}
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}
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char *pi = base + i * size;
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qswap (pi, pivot, size);
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return i;
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}
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static void
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_qsort (void *base, size_t lo, size_t hi, size_t size,
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int (*compare) (void const *, void const *))
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{
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if (lo >= hi)
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return;
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size_t pi = qpart (base, lo, hi, size, compare);
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if (pi > 0)
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_qsort (base, lo, pi - 1, size, compare);
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_qsort (base, pi + 1, hi, size, compare);
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}
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void
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qsort (void *base, size_t count, size_t size,
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int (*compare) (void const *, void const *))
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{
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if (count <= 1)
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return;
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_qsort (base, 0, count - 1, size, compare);
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}
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