mirrors/phobos
1
0
Fork 0
mirror of https://github.com/dlang/phobos.git synced 2025-04-29 06:30:28 +03:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

Faster heap operations

Browse source
This commit is contained in:
Andrei Alexandrescu 2016-01-15 11:25:28 -05:00
parent 11485b6b04
commit c12573a337
1 changed files with 34 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

44
std/algorithm/sorting.d
View file

@ -1270,18 +1270,14 @@ package(std) template HeapOps(alias less, Range)
void heapSort()(Range r)
{
// If true, there is nothing to do
if(r.length < 2) return;
if (r.length < 2) return;
// Build Heap
buildHeap(r);
// Sort
size_t i = r.length - 1;
while(i > 0)
for (size_t i = r.length - 1; i > 0; --i)
{
swapAt(r, 0, i);
percolate(r, 0, i);
--i;
siftDown(r, 0, i);
}
}
@ -1289,7 +1285,35 @@ package(std) template HeapOps(alias less, Range)
void buildHeap()(Range r)
{
size_t i = r.length / 2;
while(i > 0) percolate(r, --i, r.length);
while (i-- > 0) siftDown(r, i, r.length);
assert(isHeap(r));
}
bool isHeap()(Range r)
{
size_t parent = 0;
foreach (child; 1 .. r.length)
{
if (lessFun(r[parent], r[child])) return false;
// Increment parent every other pass
parent += !(child & 1);
}
return true;
}
//template because of @@@12410@@@
void siftDown()(Range r, size_t parent, immutable size_t end)
{
for (;;)
{
auto child = parent * 2 + 1;
if (child >= end) break;
auto child1 = child + 1;
if (child1 < end && lessFun(r[child], r[child1])) child = child1;
if (!lessFun(r[parent], r[child])) break;
r.swapAt(parent, child);
parent = child;
}
}
//template because of @@@12410@@@
@ -1305,7 +1329,8 @@ package(std) template HeapOps(alias less, Range)
if(child >= end) break;
if(child + 1 < end && lessFun(r[child], r[child + 1])) child += 1;
auto child1 = child + 1;
if (child1 < end && lessFun(r[child], r[child1])) child = child1;
swapAt(r, parent, child);
parent = child;
@ -2190,7 +2215,6 @@ auto topN(alias less = "a < b",
if (nth >= r.length) return r[0 .. $];
auto ret = r[0 .. nth];
for (;;)
{