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tupperware: vector: use more robust partition

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This one is less efficient, doing up to N comparisons. However it is not
vulnerable to the pivot being at the end or beginning of the input...
This commit is contained in:
Bruno BELANYI 2020-11-30 11:33:17 +01:00
parent efd612e0ff
commit 0888e21150
1 changed files with 10 additions and 16 deletions
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26
src/vector.c
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@ -492,24 +492,18 @@ static size_t pivot_median3_between(struct vector *v,
static size_t partition_between(struct vector *v, size_t pivot, static size_t partition_between(struct vector *v, size_t pivot,
vector_cmp_f cmp, void *cookie, struct sort_params *params) { vector_cmp_f cmp, void *cookie, struct sort_params *params) {
size_t i = params->begin; size_t l = params->begin;
size_t j = params->end; size_t r = params->end;
void *p_val = VEC_AT(v, pivot); swap_using(v, pivot, --r, params->buffer); // Put pivot at the end
while (1) { void *p_val = VEC_AT(v, r);
while (cmp(VEC_AT(v, i), p_val, cookie) < 0) {
++i;
}
do
{
j--;
} while (cmp(VEC_AT(v, j), p_val, cookie) > 0);
if (i < j) { for (size_t i = l; i < r; ++i) {
swap_using(v, i, j, params->buffer); if (cmp(VEC_AT(v, i), p_val, cookie) < 0)
} swap_using(v, i, l++, params->buffer);
else
return i + (params->begin == i);
} }
swap_using(v, l, r, params->buffer); // Put it back where it needs to be
return l;
} }
#define SMALL_THRESHOLD 10 #define SMALL_THRESHOLD 10