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Sorting algorithms/Heapsort: Difference between revisions
→{{header|Pascal}}: add example
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{HeapSort Arr}
{Show {Array.toRecord unit Arr}}</lang>
=={{header|Pascal}}==
An example, which works on arrays with arbitrary bounds :-)
<lang pascal>program HeapSortDemo;
type
TIntArray = array[4..15] of integer;
var
data: TIntArray;
i: integer;
procedure siftDown(var a: TIntArray; start, ende: integer);
var
root, child, swap: integer;
begin
root := start;
while root * 2 - start + 1 <= ende do
begin
child := root * 2 - start + 1;
if (child + 1 <= ende) and (a[child] < a[child + 1]) then
inc(child);
if a[root] < a[child] then
begin
swap := a[root];
a[root] := a[child];
a[child] := swap;
root := child;
end
else
exit;
end;
end;
procedure heapify(var a: TIntArray);
var
start, count: integer;
begin
count := length(a);
start := low(a) + count div 2 - 1;
while start >= low(a) do
begin
siftdown(a, start, high(a));
dec(start);
end;
end;
procedure heapSort(var a: TIntArray);
var
ende, swap: integer;
begin
heapify(a);
ende := high(a);
while ende > low(a) do
begin
swap := a[low(a)];
a[low(a)] := a[ende];
a[ende] := swap;
dec(ende);
siftdown(a, low(a), ende);
end;
end;
begin
Randomize;
writeln('The data before sorting:');
for i := low(data) to high(data) do
begin
data[i] := Random(high(data));
write(data[i]:4);
end;
writeln;
heapSort(data);
writeln('The data after sorting:');
for i := low(data) to high(data) do
begin
write(data[i]:4);
end;
writeln;
end.</lang>
Output:
<pre>
The data before sorting:
12 13 0 1 0 14 13 10 1 10 9 2
The data after sorting:
0 0 1 1 2 9 10 10 12 13 13 14
</pre>
=={{header|Perl}}==
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