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lib/std/sort: use Hoare's algorithm in quicksort

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Signed-off-by: Pierre Curto <pierre.curto@gmail.com>
This commit is contained in:
Pierre Curto
2023-07-11 08:27:19 +02:00
committed by Christoffer Lerno
parent 0efb142c88
commit 1ffe430df0
1 changed files with 29 additions and 16 deletions
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45
lib/std/sort/quicksort.c3
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@@ -15,32 +15,45 @@ def ElementType = $typeof(Type{}[0]);
fn void qsort(Type list, isz low, isz high, Comparer cmp)
{
if (low < high)
if (low >= 0 && high >= 0 && low < high)
{
isz p = partition(list, low, high, cmp);
qsort(list, low, p - 1, cmp);
qsort(list, low, p, cmp);
qsort(list, p + 1, high, cmp);
}
}
fn isz partition(Type list, isz low, isz high, Comparer cmp) @inline @local
{
ElementType pivot = list[high];
ElementType pivot = list[low + (high - low) / 2];
isz i = low - 1;
for (isz j = low; j < high; j++)
isz j = high + 1;
bool ok;
while (true)
{
$switch
$case $checks(cmp(list[0], list[0])):
if (cmp(list[j], pivot) > 0) continue;
$case $checks(cmp(&list[0], &list[0])):
if (cmp(&list[j], &pivot) > 0) continue;
$default:
if (greater(list[j], pivot)) continue;
$endswitch
i++;
do {
i++;
$switch
$case $checks(cmp(list[0], list[0])):
ok = cmp(list[i], pivot) < 0;
$case $checks(cmp(&list[0], &list[0])):
ok = cmp(&list[i], &pivot) < 0;
$default:
ok = less(list[i], pivot);
$endswitch
} while (ok);
do {
j--;
$switch
$case $checks(cmp(list[0], list[0])):
ok = cmp(list[j], pivot) > 0;
$case $checks(cmp(&list[0], &list[0])):
ok = cmp(&list[j], &pivot) > 0;
$default:
ok = greater(list[j], pivot);
$endswitch
} while (ok);
if (i >= j) return j;
@swap(list[i], list[j]);
}
i++;
@swap(list[i], list[high]);
return i;
}