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Reimplement QuickSort (non-recursive modification).

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Dmitry Atamanov
2023-08-22 16:46:04 +05:00
committed by Christoffer Lerno
parent 6c60b0d2a6
commit fcb4bc0781
1 changed files with 59 additions and 42 deletions
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101
lib/std/sort/quicksort.c3
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@@ -18,51 +18,68 @@ module std::sort::qs(<Type, Comparer>);
def ElementType = $typeof(Type{}[0]);
struct StackElementItem @private
{
isz low;
isz high;
}
def Stack = StackElementItem[64] @private;
// Based on https://alienryderflex.com/quicksort by Darel Rex Finley, Public Domain.
fn void qsort(Type list, isz low, isz high, Comparer cmp)
{
if (low >= 0 && high >= 0 && low < high)
{
isz p = partition(list, low, high, cmp);
qsort(list, low, p, cmp);
qsort(list, p + 1, high, cmp);
Stack stack;
stack[0].low = low;
stack[0].high = high;
isz i;
isz l;
isz h;
while (i >= 0)
{
l = stack[i].low;
h = stack[i].high;
if (l < h)
{
ElementType pivot = list[l];
while (l < h)
{
$switch
$case $checks(cmp(list[0], list[0])):
while (cmp(list[h], pivot) >= 0 && l < h) h--;
$case $checks(cmp(&list[0], &list[0])):
while (cmp(&list[h], &pivot) >= 0 && l < h) h--;
$default:
while (greater_eq(list[h], pivot) && l < h) h--;
$endswitch
if (l < h) list[l++] = list[h];
$switch
$case $checks(cmp(list[0], list[0])):
while (cmp(list[l], pivot) <= 0 && l < h) l++;
$case $checks(cmp(&list[0], &list[0])):
while (cmp(&list[l], &pivot) <= 0 && l < h) l++;
$default:
while (less_eq(list[l], pivot) && l < h) l++;
$endswitch
if (l < h) list[h--] = list[l];
}
list[l] = pivot;
stack[i + 1].low = l + 1;
stack[i + 1].high = stack[i].high;
stack[i++].high = l;
if (stack[i].high - stack[i].low > stack[i - 1].high - stack[i - 1].low)
{
@swap(stack[i], stack[i - 1]);
}
}
else
{
i--;
}
}
}
}
fn isz partition(Type list, isz low, isz high, Comparer cmp) @inline @local
{
ElementType pivot = list[low + (high - low) / 2];
isz i = low - 1;
isz j = high + 1;
bool ok;
while (true)
{
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;
$if $checks(list.swap(0, 0)):
list.swap(i, j);
$else
@swap(list[i], list[j]);
$endif
}
}