fix qsort

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Jan (janneke) Nieuwenhuizen 2022-10-25 15:46:55 +02:00
parent 2901f98fce
commit 80956130b8
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1 changed files with 27 additions and 36 deletions

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@ -19,69 +19,60 @@
* along with GNU Mes. If not, see <http://www.gnu.org/licenses/>.
*/
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#if 1
static void
qswap (char *a, char *b, size_t size)
{
while (size-- > 0);
while (size-- > 0)
{
char tmp = *a;
*a++ = *b;
*b++ = tmp;
}
}
#else
static void
qswap (void *a, void *b, int size)
{
assert (a != b);
char buffer[size];
memcpy (buffer, a, size);
memcpy (a, b, size);
memcpy (b, buffer, size);
}
#endif
static size_t
qpart (char *base, size_t count, size_t size,
static int
qpart (char *base, int lo, int hi, size_t size,
int (*compare) (void const *, void const *))
{
void *p1 = base + count * size;
size_t i = 0;
for (size_t j = 0; j < count; j++)
char *pivot = base + hi * size;
int i = lo - 1;
for (int j = lo; j < hi; j++)
{
char *p2 = base + j * size;
int c = p1 == p2 ? 0 : compare (p2, p1);
if (c == 0)
i++;
else if (c < 0)
char *pj = base + j * size;
if (pj != pivot && compare (pj, pivot) < 0)
{
char *p1 = base + i * size;
qswap (p1, p2, size);
i++;
void *pi = base + i * size;
qswap (pi, pj, size);
}
}
char *p2 = base + i * size;
if (p1 != p2 && compare (p1, p2) < 0)
qswap (p1, p2, size);
i++;
char *pi = base + i * size;
qswap (pi, pivot, size);
return i;
}
static void
_qsort (void *base, int lo, int hi, size_t size,
int (*compare) (void const *, void const *))
{
if (lo >= hi || lo < 0)
return;
int pi = qpart (base, lo, hi, size, compare);
_qsort (base, lo, pi - 1, size, compare);
_qsort (base, pi + 1, hi, size, compare);
}
void
qsort (void *base, size_t count, size_t size,
int (*compare) (void const *, void const *))
{
if (count <= 1)
return;
size_t p = qpart (base, count - 1, size, compare);
qsort (base, p, size, compare);
char *pbase = base;
char *p1 = pbase + p * size;
size_t c1 = count - p;
qsort (p1, c1, size, compare);
_qsort (base, 0, count - 1, size, compare);
}